retaining walls surrounding the Mount, but also rebuilt the arches of the "Great Bridge". Dimensions The Arch was measured by Wilson, who noted that its crown reaches a height of above bedrock, its span being of . Only a portion of the Arch is visible today. A square shaft cut down under the arch allows sighting of the wall's original massive foundations, "with fourteen courses of dressed stone below the present ground level." The exact dimensions of the Second Temple period bridge which stood over the arch are impossible to determine. Discovery and excavation Titus Tobler noted the structure and wrote in 1853 that "I regard the vaults as supporting arches for the path or bridge that leads from Suk Bab es-Sinsleh to Bab es-Sinsleh". The arch was scientifically documented for the first time in 1865 by explorer and surveyor Charles Wilson, for whom it was named. Wilson had joined the Ordnance Survey of Jerusalem in 1864, continuing to participate in the city surveying project that was established to improve the city's water system. Not long after Wilson, Charles Warren excavated under the arch by digging two trial shafts, one along the western pier all the way down to bedrock. He published his discoveries in 1876. In 1968, only a few months after the Six-Day War, Israel began excavations to uncover the portion of the Western Wall that was not exposed. As the excavations continued, the opening to the arch was uncovered, and rubble began to be removed. It would take 17 years, until 1985, until the entire length of the wall would be cleared. The space under the arch was fitted out after 1967 as a synagogue, with a new floor built over the floor of a large Mamluk-Ottoman water reservoir, called by Warren 'Pool Al Burak'. The presence of the synagogue restricted further excavation under Wilson's Arch to a large degree, with limited digs being carried out in 2006 and 2011, followed by a substantial dig between 2015 and 2018 over a 200 m³ total area. This large project focused on dating the arch and, after exposing a theatre-like structure directly beneath it, the date and function of this unexpected finding. Associated structures Herodian "Western Stone" The Western Stone, located in the north section of the Arch, is a monolithic stone block forming part of the lower level of the Western Wall. Weighing 570 tonnes (628 tons), it