When Herod extended the courts Josephus tells us that Herod used lead to bind the foundations of his wall to give it great strength.

"He also built a wall below, beginning at the bottom, which was encompassed by a deep valley; and at the south side he laid rocks together,
and bound them one to another with lead, and included some of the inner parts,"

I began to think about the problem he would have had with the straight joint where the old solomon wall ended and his new wall began.  Perhaps he used lead there also, to knit the two together and strengthen the joint.  If the wall began to fall would that act like a hinge and bend rather than break?   Suddenly cistern #7 looked suspiciously like a sort of hinged wall and the two sections extending to the east at the top of it reminded me an awful lot of the H shaped cistern, #14, by the Golden gate.
 

I went back and read Warren and Wilson's description of #7 cistern;  "Cistern No. VII, east of the Great Sea, descended; 62 feet deep, 2 feet 6 inches water. The construction of this cistern is very curious, at one side there is a lofty chamber having two entrances and raised 6 feet above the general level, and in the south-eastern branch four steps lead up to a small flat platform, as to the altar of a church;
on descending, the entrance of a rock-cut water conduit was seen, and this was afterwards found to communicate with the general system in this part of the area; there are two mouths, close together, with an opening between them, now roofed with fragments of marble columns; the roofing is of rock. On the cement a number of white hands were painted, probably as a charm against evil spirits.    Rock 2411 feet; at 5 feet from surface."

Five feet under the surface!  That meant that this cistern was not at a level with the big E cistern , # 11, but was instead at a level more to that of Solomon's Porch, meaning it was not a cistern originally but in fact was ruins of the temple, namely a bottom structure of the porch of Solomon and east wall extention of Herod.  Since the ground level (bedrock) at this point rises dramatically northward toward the Dome plateform but also dropped severly to the east then a structure would have been built by Herod to reinforce this new section of the east wall.  I don't know if this new section connected into Solomon's porch at one time or just was braced against it.
 

My idea is that something catastrophic caused the eastern wall to begin to buckle inward at the straight joint,  where the northeast corner of Solomon's old wall and Herod's extention that wall began, but because of the lead used in the joining of the walls it didn't crumble but instead the southern section of it section began to collaps  and swing outward, and downward, hanging over the hill.  After further examining the maps  I have come to believe, as one other of the people who has a website concerning the mount and Temple, that the great sea, which is also at a level close to the surface, is ruins of buildings rather than a cistern dug by the early Hebrews. It appears to me that there was a very, very, large cistern in this area, much like the collapsed one in the Ophel ruins, and like the southern one this northern cistern collapsed also. The great sea would now be made up of the large buildings that collapsed into this old cistern below. We see the same sort of results when a large sink holes opens up in this country and a house falls into it. When the buildings collapsed into this old cistern they twisted, and with the rotating tool in a paint program one can rotate both the great sea and the Ophel ruins 17 degrees and the east to west walls  within the ruins once again line up with the rest of the Temple compound. It seems the Hebrews had hollowed out much of the area outside the bounds of Solomon's temple compound, with smaller portions of these large cisterns under the temple compound area as a water source within if they were laid siege upon. Water was like gold in Israel, as it is today.  And if attacked, the whole city of David may have had to go into the Temple compound and survive for many, months, if not a few years. So water and much food storage in the temple was needed.  (I added a picture of a cistern at the bottom of this page.)

When I look at the Ophel collapse I can see that everything to the east of the collapsed twisted area also fell and moved quit a few feet being drawn toward the twisted mass as it sank.  It appears that the same sort of action took place east of  the great sea area drawing the buildings of # 7, so called cistern,   toward the old "great cistern" as it collapsed.  Most likely this happened during, or very soon after, the burning and destruction of the Temple compound. Perhaps an earthquake.  I don't think a section of the east wall could have moved in such a way after the area was filled in with dirt.   The Roman's wouldn't be able to disassemble such a large section of wall, with colonnade, because of the danger involved, with the low section actually hanging out over the edge of the hill, but instead they  built up an existing  Hasmonean lower wall that ran along the base of the hill.   Once this wall was built to a very high wall and the south east corner built up with terraced rooms to save the amount of fill dirt needed, they then filled up the hollows with dirt and rubble from the destroyed compound and city and surrounding area.
 

 I took the map into a paint program and began to dissect it like a puzzle.  Using the rotate tool I rotated the bottom arm of # 7 cistern and inserted it back into the map.