1000 to 1049






A shows a tube shape at 9 o’clock, at 8 o’clock there are patches or tubes on the roof of the hollow hill. At 7 o’clock there is a large tube going directly to a small crater and terminating at it, there may also have been an extension of this going to the large crater beyond it. B at 2 o’clock shows the edge of the hollow hill with a tube just above it. At 1 and 6 o’clock there is a large wall or tube in a parabolic shape, 8 and 9 o’clock show other tubes. C at 5 and 7 o’clock shows this parabolic ridge or tube, at 1 and 3 o’clock is another tube. D shows another tube. E at 1 o’clock shows the parabolic tube and at 3 o’clock some disconnected tubes.







B at 2 o’clock is the start of a ridge or tube, this is also close to the axis of symmetry of the parabola extending to the right. There is a small hill near the apex of the parabola in line with this axis of symmetry which may have been used to construct it accurately. B at 9 o’clock also points to a straight tube like a chord from one side of the parabola to the other. This may have gone through the focus, drawing on top of an image like this would have some inaccuracies. It may have been used to help construct the shape. B at 8 o’clock would be close to going through the focus as drawn. Other lines and tubes may have been intended to measure where the parabolic tube would go. This would be an easier construction technique to create a parabola, the tubes would have a known length further up and at right angles to the axis of symmetry.







A shows degraded wavy tubes at 9 and 10 o’clock, at 4 o’clock a tube goes into a crater. B shows tubes at 3 and 8 o’clock, at 2 and 4 o’clock is like an intact part of the hollow hill roof. C, D and E show the former pit wall of the hollow hill.







These hills have unusual shapes on their roofs like tubes or patches, A shows a tube shape going to a crater from 2 to 12 o’clock, at 3 o’clock it shows a tube on both legs. At 5 o’clock on the second leg there is a tube and a tube intersection, then it goes to the left in a tube network. B shows the edge of a roof in possibly a settled area, at 2 and 6 o’clock the roof skin may have peeled off. C at 12 o’clock also looks like the skin has peeled off in a large area, this connects back to the hollow hill under C through 1 o’clock. D also shows a step like peeled skin as does E. F shows another tube as does G.







A shows a degraded side of a hollow hill with a cavity running horizontally along at, B at 12 o’clock shows the edge of an intact roof segment, another edge is at 10 o’clock. At 2 o’clock there is a faint tube connecting to a small hill. At C at 10 o’clock there are some small cavities, also a tube network at 7 o’clock. Perhaps at 11 o’clock there is a collapsed hollow hill.







These formations may also be hollow hills, A shows a flat angular roof, B shows a tube at 8 o’clock, a tube intersection at 3 o’clock, and a small shape connecting to a degraded tube going off to the left. C shows a tube at 9 o’clock, and the darker edge of the roof at 2 o’clock. D shows another tube, E also shows a degraded tube on the roof at 5 o’clock and a settled area at 4 o’clock. F shows a small hill with a tube going up and down from it at 9 o’clock, also another possible tube at 6 and 7 o’clock. At 2 o’clock there appears to be a tube connecting the two hills. G shows another tube.







A shows tubes in 2 locations, B shows a tube at 7 o’clock and degraded tubes at 1 and 3 o’cl







A shows swirls on the roof of this hollow hill, perhaps layers or interior supports in the shape of an arch. Between A and C the arcs are approximately evenly spaced, have a similar albedo and width. C shows a tube at 10 o’clock, also a tube like connection between these arcs at 11 o’clock.










This hollow hill is fairly symmetrical in shape, A shows a settled area where the roof may have collapsed. B shows another settled area.







A shows more of these arcs on the roof of a hollow hill as does B. At 8 and 10 o’clock the arcs are similar to Prhh1014. C shows a collapsed hollow hill, the dark areas may have been patch repairs at some stage.







Many tubes come out of this formation, A at 8 and 9 o’clock shows a tube intersection. At 3 o’clock is another tube from the pit wall. B shows two more tubes, below the one at 4 o’clock are two small enclosures, also another two between there and C at 8 o’clock. These may all be dams including the large pits. C at 7 o’clock shows many faint tubes coming out of the pit wall. D at 9 o’clock shows the pit wall is doubled with a groove between them. At 5, 6, and 7 o’clock the pit wall is very even and rounded, at 3 o’clock is another tube coming out of the pit wall. E at 12 o’clock shows one of the pale formations inside the pit, these may have been hollow hills and have a similar albedo to parts of the pit walls. At 2 and 9 o’clock the pit wall gets thicker, this part has a roof like a tube but to the right and left it becomes a groove again. It’s likely then most of these pit walls are hollow.







An unusual shape looking like a leaf, this is near the Ferns so it may be related to them. A and B show straight grooves parallel to each other, these connect to C which are also parallel to each other. The spacing between the grooves, the depth of the grooves and their overall shape remain consistent throughout the image. The groove at A appears to connect to a tube shape at F at 4 and 7 o’clock, which then ends near a tube shape at right angles to it. This closes the parallel lines at C.  E shows other tubes on the formation, D shows there is a groove around the leaf shape with a consistent depth and albedo.







This shows the leaf shape is formed by a double parabola, the tube at E at 2 o’clock divides the parabolic shape in half. F can be regarded as a chord or line which connects the two parabolas, this may have geometric significance. There are also shapes which may have defined the foci and a line between them on their respective axis of symmetries. If the parabolas were moved a small distance to the right they would still be consistent with the leaf shape and this may then connect the foci. The arrangement of the parallel lines and the double parabolas may mean this is some kind of geometric statement overall.







This appears to be a collapsed hollow hill, A shows the hill wall foundations. A also shows the edge of this wall, both may indicate a double wall extended into the roof. Some of these may have had a parabola shape and so an inner and outer parabola may have formed the roof like in many of the crater dams. C shows the wall is sharp at 9 o’clock as if broken off. This may have been part of the skin of perhaps cement that covers many of the hollow hills. D shows a long part of the pit wall, this may have been an entrance into it. E at 2 o’clock shows the wall is doubled here with a thin groove running along it. At 9 and 12 o’clock this may be the pit wall of a former separate room in the hollow hill, there may have been an entrance between 12 and 2 o’clock. F looks like another small room.







This shows an ellipse and approximate circle connected with grooves, A at 7 and 8 o’clock forms a tangent to the ellipse that intersects another tangent 4 and 7 o’clock. These tangents are close to the major and minor axis of the ellipse and again may be a geometric statement. A at 6 o’clock second leg shows another groove or road connecting to the circle. B shows the sides of this ellipse at 10 and 12 o’clock, at 2 and 4 o’clock there are many grooves which may have been tubes or roads.

C, D, E, and F show many more of these coming out of the circle, they do not seem to be a random chaos or series of cracks but come out of the circle perhaps as roads. G shows an inner wall of the circle at 7 and 11 o’clock, a similar wall for the formation at 2 o’clock. These may have been dams or for growing crops such as rice that required a shallow wall around them to hold in water. H and I show more of these walls and shallow pits. This is little evidence to show what these were for, but they do seem to have a special purpose which is likely to be food related.





This overlay shows how close the ellipse is to a perfect geometric shape. The circle on the right is also partially elliptical but as can be seen is also close to perfect. The curved shapes in it may give an optical illusion that its boundary was more irregular. The small deviations may have occurred from the edges subsiding or eroding, also the ground could have moved in this area deforming both shapes.







This seems to be another pit, the unusual shape might have represented a comet. There is an impression of parallel ridges coming out of the hill in the left end like a comet’s rays. It is however more curved than a comet would usually be, A shows the pit wall and how it connects to the possible collapsed hollow hill below it. B shows a pit wall between 9 and 10 o’clock with a dividing ridge or interior support inside it like a collapsed hollow hill. At 3 o’clock there is a gap in the pit wall where another hollow hill may have been. At 4 o’clock there are more road shapes connecting the formations. C shows another sharp pit wall like the former skin of a hollow hill. D shows more of this as does E.







This may also be a collapsed hollow hill, A, B, and C appears to be pit walls. D shows a hollow area at 4 o’clock, a connection to a crater at 9 o’clock, and possible interior supports at 7 o’clock. E may also be walls of a former hill.






A shows some rounded pits, these may also have been used for farming. At 4 o’clock second leg there are tubes connecting into a crater. B at 10 o’clock shows another rounded shape like a pit wall, at 4 o’clock is a tube connecting down to a tube at D and another one at E. F shows other tubes, G shows the hill walls of the collapsed hollow hill at 6 and 10 o’clock, the interior supports would be at 8 o’clock. H shows tubes going into a crater.







A, B, and C appear to be a tube, at 8 o’clock there is a collapsed segment  in the tube roof. It becomes thinner at 4 o’clock, at B at 11 o’clock there also appear to be collapsed segments in the tube roof. At 2 and 3 o’clock there may have been a hollow hill. C shows a tube connection to a hollow hill below it.







A is a pit that may also have been a hollow hill, at 7 o’clock there is a tube or part of the hill wall dividing the area on the left into a separate room. B shows an unusual crater with concentric rings and perhaps an interior support in the center like a collapsed hollow hill.







A shows the edge of a pit at 10 o’clock, at 1,2, and 4 o’clock are pit walls perhaps intended to act as dams. At 5 o’clock there is a faint wall perhaps eroded. B shows another eroded wall at 10 and 11 o’clock, at 8 o’clock is a curved tube or pit wall, and at 7 o’clock is an eroded tube. C at 8 o’clock shows a channel or groove connecting to the pit walls perhaps to direct water along it. At 3 and 7 o’clock are more walls or tubes. D also shows another tube or pit wall. E shows a small tube coming out of a hill with a collapsed roof. F shows more tubes or pit walls. G shows a small pit with a curved wall inside it, perhaps a former interior support.







A may show more walls or tubes in a T intersection. B shows other walls or tubes, C is an eroded tube that foes into two craters then extends to the right connecting to A. D shows more possible eroded tubes including a tube intersection.







A shows the pit wall of a possible collapsed hollow hill, B shows other parts of this pit wall. At C the wall is more eroded. D shows eroded tubes near an interior support.







This shows how part of the pit wall is a parabola.







These also appear to be constructed walls, perhaps including farming areas. At A at 3 o’clock the wall is much thicker with an internal cavity between it and C at 10 o’clock. At A at 8 o’clock there is a smooth sloped wall enclosing the rougher terrain inside it. B shows the internal walls of this formation, they also slope down to the rougher terrain without being the same kind of construction technique. They then remain smoother on the inside and outside. C shows another enclosure between 5 and 9 o’clock but with a smooth floor as does D. The difference between the interiors implies a different purpose, below B there is another pit with a much smoother and sloping floor. These different types of pits may have been used for a process of farming, fishing, etc where either the produce was moved from one to another or they were used for different purposes. E shows a curved tube going into the pit wall.







A shows a pit wall at 7 o’clock with an angular walled segment, rounded inside it. From 2 to 5 o’clock this may be a large collapsed tube going into the crater, to the right of this above B it seems to merge into a more intact roofed segment. B shows a smooth slope to the wall in this segment, C shows a curved tube that goes around in a loop. To the left of C at 10 o’clock is a groove which may have a collapsed roof extending to the left into a hollow formation.







This shows how the left side is a parabola.







A and B shows the edges of a nearly symmetrical platform, perhaps there was a hollow hill on it. It is composed on multiple layers, perhaps of concrete, and may connect to the crater on the left.







A at 12 o’clock shows a long dark line like a road which connects to D at 10 o’clock, where it becomes a tube. At 2 o’clock D shows a tube connecting to it, A at 4 and 5 o’clock show other dark lines. B shows another dark line merging into the main one, these are unlikely to be dust devil tracks because they are so straight. There is also a right angled tube or wall from B at 10 o’clock to A at 11 o’clock.







A shows a curved tube with a narrow roof, the cross section would be like a triangle. B shows a cavity at 10 o’clock like a collapsed hollow hill which may have extended down to C. At 1 o’clock B shows a part of the intact roof. C shows another tube or part of the hill wall. D shows parts of the former hill.







This shows how two of the curved tubes are in the shape of a parabola at right angles to each other.







A may be a collapsed hollow hill, the wall or a tube is shown at 4 and 7 o’clock. At 11 and 2 o’clock there is the darker material with a sharp boundary around the pit. B shows another probable pit wall, like at A it has regular grooves across it as if it is eroding between interior supports along it. C at 2 o’clock shows another wall, at 10 o’clock is another cavity. D shows another wall or tube at 5 and 10 o’clock, 1, 2, and 4 o’clock show more likely roads. E shows more roads, tubes, or pit walls.







These walls are also like parabolas.







A and B show curved walls or tubes. C shows a cavity like a collapsed hollow hill. D shows another degraded wall.







The two curved walls form parts of parabolas.







A looks to be another wall or tube, B at 10 o’clock shows a tube and at 4 o’clock a pit which may have been a hollow hill. C shows a dark line like a road at 12 and 2 o’clock, at 10 o’clock is a long ridge like a pit wall for the depression to the left of it. D shows a wall or tube at 2 and 6 o’clock, at 12 o’clock there are walls or tubes on both legs. E shows another section of the wall at 8 o’clock, at 4 o’clock is a pit which may have been a hollow hill.







A, B, and C show what may be tubes coming out of the dark material. This may be a habitat, there may be tunnels or corridors under it and tubes leading out to the right.







A shows more of these dark lines, they may be grooves in the material like roads. B shows other roads, one goes into the elliptical pit at 4 o’clock. C shows more of these, D at 9 o’clock shows a tube or road going into a hollow hill shape which may have collapsed. At 7 o’clock is a tube also going up to the ellipse though 12 o’clock. E shows more roads.







This is a closeup of the ellipse, A shows a wall separating the upper and lower pit segments. B shows a pit wall at 9 o’clock, at 12 o’clock there is a dark road, and at 1 o’clock there is a pit wall. C shows the pit walls, D shows tubes going into the ellipse, and E show the pit wall.







A shows another pit wall, it also has regular grooves across it like the material between the supports has collapsed. It might then be like posts where the material between them has eroded away leaving a series of regular spacings. B is a right angled tube, C is a pit wall in better condition, D shows another wall connecting to C and over to A.







This shows how part of the formation is a parabola.







The outer pit wall also fits well into a parabola.







A shows a probable road that comes to a T junction at D, B shows one of these roads going through a pit up the image. A from 9 to 5 o’clock closely bisects the large pale pit which has some symmetry, this may have lost some of its shape due to erosion. C shows a dark line like a curved road.













A shows some walls in close to right angles between them. B shows more walls, at 2 o’clock the slope is very even as is the height of the wall. At 7 o’clock and beyond there are many walls intersecting at right angles. C shows a cavity at 1 o’clock and 2 o’clock perhaps from a collapse, at 4 o’clock there is a curved wall or tube. D shows another possible tube, E shows a tube or wall intersection at 12 o’clock, more walls at 2 o’clock and a pit wall at 9 o’clock.







Many of these curved walls form parabolas as shown.







This shows another series of pits or dams, A looks to be a collapsed hollow hill with a wall off at 2 o’clock. B shows another wall segment with a smooth slope as does C. D shows how the interior of this pit is much smoother than outside, as if the external erosion forces like water have been kept out. It implies then this has remained largely sealed with some material slowly coming in from the entrances at the top of the pit such as at E. F shows another pit which seems more concave, G shows walls or tubes connecting to it.






Part of the pit fits to a parabola as shown.







The other pit also closely fits to two parabolas with parallel latis rectums.







This is a closeup of A in the previous image, A, B, and C here show degraded parts of the roof beginning to collapse. It’s likely the cavity at B from 3 to 4 o’clock was covered by a roof at one stage.







B also appears to have been hollow, A at 1 o’clock shows a long cavity like a tube. At 6 o’clock may have been the base of a hollow hill.







This also appears to have been a hollow hill, A at 6 o’clock shows a cavity with an entrance along this line. B at 1 o’clock shows another cavity, it gives some insight into how wide the cavities could be to support a roof. At 2 o’clock there is a settled roof segment, this may be hollow underneath. At 5 and 7 o’clock this hollow is about the same width as B at 1 o’clock.







A shows a long tube or wall, the slope is fairly even along it as is its texture and width. B at 4 and 7 o’clock is more eroded but has a similar slope, at 10 o’clock there is a series of right angles where there may have been walls. C shows a tube at 6 o’clock and a wall at 3 o’clock. D shows a straight edge to this smooth area, perhaps there was a tube here like A. E also shows a wall, the slope indicates this cavity may have been covered by a roof.







A at 6 o’clock is smooth like cement, this may have been a room inside a hollow hill. At 2 and 8 o’clock is an edge in the ground like where the wall extended to. B at 9 o’clock shows a jagged wall as if the roof broke off. At 11 and 1 o’clock there is a groove running along the inside of the wall. C shows a cavity like an entrance at 9 o’clock, at 12 and 2 o’clock may have been the hollow hill wall. D shows the wall is more eroded here with some segments apparently broken off.






These pits may also have been hollow hills or dams, A shows a sharp pit wall. B also shows walls that form depressions that could have held water like a dam. C shows an elevated segment which may have been part of a wall. D also looks like a pit that extended down into B, perhaps for farming. E is a similar pit wall. F at 9 o’clock shows a squarish depression, a tube at 12 o’clock, and a pit wall at 8 o’clock. G shows a rounded pit at 8 o’clock, another pit at 10 o’clock, and a raised section with a rounded dark patch on its roof like a hollow hill.







A shows the edge of the pit at 7 o’clock, at 5 o’clock there may be a collapsed part of the roof around this raised area like a hollow hill. B shows the edge of this hill which becomes a wall or tube at the top of the image. At 4 and 7 o’clock the edge of the pit is steep and in good condition here. C and F are also parts of this pit wall, ay F at 7 o’clock there is a curve in the wall similar to some dams. E shows a pit that becomes a groove or canal to the right.







A shows another pit wall at 2 o’clock, at 5 o’clock is another pit wall. At 9 and 10 o’clock are smaller pits which may have been used for farming. B shows more of these pit walls as does C and D. E at 8 o’clock shows unusual patterns in the pit, not like material that has been blown into and washed into it. At 6, 10, and 12 o’clock are more pit walls. F shows a possible tube at 4 o’clock, G shows more pits.












A at 1 o’clock shows a road, at 2, 4, and 5 o’clock may be a habitat, on the second leg of 4 o’clock is another wall. B shows more roads, at 7 o’clock second leg may be another wall. C shows more roads. D shows walls, E is a cavity from a former hollow hill or perhaps a dam, below 5 o’clock is a smooth material like a former hollow hill roof. F shows more walls.







This pit has a much smoother floor to it, perhaps sealed with cement. A, B, C, and D show pit walls that are of consistent height, width, and general shape.






This shows more pits, the pit walls shown are consistent in shape.







These are similar pits but here they are formed by walls, A shows a thicker wall at 9 o’clock dividing two pits. At 10 o’clock the wall is much thinner but the walls generally are about the same albedo and thickness not varying randomly. B at 9 o’clock shows another of these walls, at 2 and 5 o’clock there is a long narrow pit with similar walls. C shows more pit walls. The shapes are similar to Prd1046, even though each must be formed in a different way. In one image there are pits in the actual ground, in another the pits are formed with a wall. It is unlikely two dissimilar processes would be forming the same shapes next to each other, but this is consistent with the inhabitants buildings these pits for some purpose.



angular walled segment, 25

apex of the parabola, 2

arch, 7

arcs, 7, 8

axis of symmetries, 11

axis of symmetry, 2

canal, 46

cavities, 4, 42

cavity, 4, 27, 29, 30, 37, 40, 41, 42, 43, 44, 49

cement, 12, 44, 49

channel, 20

chord, 11

circle, 13, 14

collapse, 37

collapsed, 7, 33, 46

collapsed hollow hill, 4, 8, 12, 15, 16, 17, 19, 22, 27, 29, 30, 39

collapsed roof, 20, 25

collapsed segment, 18

collapsed segments, 18

collapsed tube, 25

comet, 15

concave, 39

concentric rings, 19

concrete, 26

construct, 2

constructed walls, 24

construction technique, 2, 24

corridors, 32

crater, 1, 2, 3, 16, 17, 25, 26

crater dams, 12

craters, 21

curved road, 36

curved tube, 20, 24, 25, 27

curved tubes, 28

curved wall, 20, 37

curved walls, 30, 31, 38

dam, 45, 49

dams, 9, 13, 20, 39, 45, 46

dark patch, 45

degraded tube, 5

degraded wall, 30

degraded wavy tubes, 2

disconnected tubes, 1

double parabola, 11

double parabolas, 11

double wall, 12

ellipse, 13, 14, 33

elliptical, 14

elliptical pit, 33

enclosure, 24

enclosures, 9

entrance, 12, 42, 44

entrances, 39

eroded tube, 20, 21

eroded tubes, 21, 22

eroded wall, 20

faint tube, 4

faint tubes, 9

faint wall, 20

farming, 17, 24, 45, 47

farming, fishing, 24

Ferns, 10

flat angular roof, 5

floor, 49

foci, 11

focus, 2

geometric statement, 11, 13

groove, 9, 10, 12, 13, 20, 25, 44, 46

grooves, 10, 13, 29, 33, 34

growing crops, 13

habitat, 32, 49

hill wall, 19, 27

hill wall foundations, 12

hill walls, 17

hollow, 9, 16, 25, 41, 42

hollow hill, 1, 3, 4, 7, 8, 12, 15, 18, 19, 26, 31, 33, 41, 42, 44, 45, 46, 49

hollow hill roof, 3, 49

hollow hill wall, 44

hollow hills, 5, 12, 45

inhabitants, 51

inner and outer parabola, 12

inner wall, 13

intact roof, 27

intact roofed segment, 25

interior support, 19, 20, 22

interior supports, 7, 16, 17, 29

internal cavity, 24

internal walls, 24

intersecting at right angles, 37

intersects another tangent, 13

jagged wall, 44

layers, 7

leaf, 10, 11

major and minor axis, 13

multiple layers, 26

optical illusion, 14

or interior support, 15

parabola, 2, 12, 23, 25, 28, 35, 36, 39

parabolas, 11, 29, 31, 38, 40

parabolic, 1

parabolic ridge or tube, 1

parabolic shape, 11

parabolic tube, 1, 2

parallel latis rectums, 40

parallel lines, 10, 11

parallel ridges, 15

patch repairs, 8

patches, 1, 3

peeled off, 3

peeled skin, 3

pit, 9, 15, 19, 20, 24, 29, 31, 36, 39, 40, 45, 46, 47, 49, 51

pit segments, 33

pit wall, 9, 12, 15, 17, 20, 22, 23, 24, 25, 29, 31, 33, 34, 36, 37, 45, 46, 47

pit wall of the hollow hill, 3

pit walls, 9, 16, 20, 29, 33, 47, 49, 50, 51

pits, 9, 24, 39, 45, 47, 50, 51

posts, 34

Prd1033, 39

Prd1034, 43

Prd1036, 44

Prd1037, 45

Prd1039, 46

Prd1040, 47

Prd1041, 48

Prd1042, 49

Prd1044, 49

Prd1046, 50, 51

Prd1049, 51

Prhh1000, 1

Prhh1000a, 1

Prhh1001, 2

Prhh1004, 3

Prhh1006, 4

Prhh1007, 5

Prhh1014, 7, 8

Prhh1015, 7

Prhh1016, 8

Prhh1018, 9

Prhh1019, 10

Prhh1019a, 11

Prhh1020, 12

Prhh1021, 13

Prhh1021a, 14

Prhh1022, 15

Prhh1023, 16

Prhh1024, 17

Prhh1026, 18

Prhh1027, 19

Prhh1028, 20

Prhh1029, 21

Prhh1030, 22

Prhh1030a, 23

Prhh1031, 24

Prhh1031a, 24

Prhh1031a2, 25

Prhh1031b, 26

Prhh1031c, 27

Prhh1031d, 27

Prhh1031d2, 28

Prhh1031e, 29

Prhh1031e2, 29

Prhh1031f, 30

Prhh1031f2, 31

Prhh1031g, 31

Prhh1031h, 32

Prhh1031i, 33

Prhh1031j, 33

Prhh1031k, 34

Prhh1031k1, 35

Prhh1031k2, 35

Prhh1031l, 36

Prhh1032, 37

Prhh1032a, 38

Prhh1033a, 40

Prhh1033a1, 39

Prhh1033a2, 40

Prhh1033b, 41

Prhh1033c, 42

Prt1010, 6

regular spacings, 34

right angled tube, 27, 34

right angles, 10, 28, 37, 43

road, 13, 15, 27, 31, 33, 36, 49

roads, 13, 29, 33, 36, 49

roof, 1, 3, 5, 7, 8, 9, 12, 27, 40, 42, 43, 44, 45, 46

roof segment, 4

roof skin, 3

roofs, 3

room, 12, 19, 44

rounded pit, 45

rounded pits, 17

settled, 3, 5, 7

settled roof, 42

shallow pits, 13

shallow wall, 13

skin, 3, 12, 15

sloping floor, 24

smooth floor, 24

smooth slope, 25, 39

smooth sloped wall, 24

squarish depression, 45

straight grooves, 10

straight tube like a chord, 2

supports, 34

symmetrical, 7

symmetry, 36

T intersection, 21

T junction, 36

tangent, 13

tangents, 13

the pit wall, 15

tube, 1, 2, 3, 5, 7, 9, 10, 11, 17, 18, 19, 20, 27, 29, 31, 33, 37, 41, 43, 45, 46, 47

tube connection, 18

tube intersection, 3, 5, 9, 21

tube network, 3, 4

tube roof, 18

tubes, 1, 2, 3, 9, 10, 13, 17, 20, 21, 29, 30, 31, 32, 33, 39

tunnels, 32

two parabolas, 11

wall, 1, 12, 13, 22, 24, 25, 27, 29, 31, 33, 34, 37, 39, 43, 44, 45, 46, 49, 51

wall intersection, 37

wall segment, 39

walls, 13, 16, 20, 21, 29, 31, 37, 39, 43, 45, 49, 51