Entering a tunnel at the prayer plaza, one turns northwards into a medieval complex of subterranean vaulted spaces and a long corridor with rooms on either side. Incorporated into this complex is a Roman and medieval structure of vaults, built of large dressed limestone. It includes an earlier Herodian room, constructed of well-dressed stones, with double openings and walls decorated with protruding pilasters. Ch. Warren, who surveyed the area in the 19th century, erroneously named it the “Masonic Hall.”

The vaulted complex ends at Wilson's Arch, named after the explorer who discovered it in the middle of the 19th century. The arch, supported by the Western Wall, was 12.8 m. wide and stood high above the present-day ground level. Josephus Flavius mentions a bridge which connected the Temple Mount with the Upper City to the west during the Second Temple period. This bridge once carried water via a conduit from Solomon's Pools; it was destroyed during the Jewish Revolt against Rome (66-70 CE) and rebuilt during the early Islamic period.

Beyond Wilson's Arch, a large cruciform hall, part of a Mamluk period construction, was cleared of debris and a large water cistern was removed, revealing the Herodian Western Wall in its full glory.

From this point, along the outer face of the Herodian western wall of the Temple Mount, a long narrow tunnel was dug slowly and with much care under the supervision of archeologists. As work progressed under the buildings of the present Old City, the tunnel was systematically reinforced with concrete supports. A stretch of the western wall — 300 m. long — was revealed in pristine condition, exactly as constructed by Herod.

At the end of this man-made tunnel, a 20 m. long section of a paved road and an earlier, rock-cut Hasmonean aqueduct leading to the Temple Mount were uncovered. Today one can proceed along it to a public reservoir and from there, a short new tunnel leads outside to the Via Dolorosa in the Muslim Quarter.