Rabbinic Tunnel, Master Course. Detail of the largest of the known stones of the Herodian supporting wall. It is said to be the size of a city bus. It is 45 feet [13.7 m.] long, 11 feet [3.5 m.] high, and about 15 feet [4.5 m] wide. It is estimated to weigh 630 tons! It is proposed, that this massive stone was used at this point because of some hollow area(s) behind it. The carved rectangular depressions in the stone were made in a later era when the area on this side of the stone was used as a cistern. The later builders inserted short pieces of wood into the depressions, and these in turn were used to help the hydraulic plaster adhere to the surface of the Herodian stone.