The Temple Mount in Jerusalem is a site with a long history of ritual importance, commencing with the Iron Age (10th cent. BCE) when King Solomon built a temple on this site. Throughout the following periods, the mount was used, almost continually, as the site of three Jewish temples (Solomon, Neherm'ah, Herod), a pagan temple (Roman Period), as the site of Islamic mosques and holy place (from 8th cent. CE onwards), and for a short period as a Christian site (during the Crusader period). For centuries, the site has been of utmost religious importance, in particular to the Jews and Moslems, and to a lesser extent to the Christians. Both the Temple Mount itself and its immediate surroundings contain numerous finds of great archaeological and historical importance.
Since the Roman period (2nd CE), Jews did not have access to the Temple Mount. In light of this, the Western Wall, the closest spot to which they could approach the original position of the destroyed Jewish temples, became one of the most important places of worship for the Jews. The Western Wall is but one of the four monumental enclosure walls surrounding the Temple Mount, which were originally built in the 1st BCE - 1st CE by Herod the Great, King of Judea. At that time, Herod extensively expanded the Temple Mount, turning it into one of the most majestic religious sites in the Roman East. Though the Temple Mount underwent numerous destructions and rebuildings since the Herodian period, the course of the four enclosure walls (including the Western-Wall) has basically gone unchanged.
The Western Wall Tunnels project commenced following the Six-Day War, as an effort to expose additional portions of this wall, in order to learn more about both the wall itself and the various structures in its vicinity of various periods. Till then, only a small portion of the wall had been exposed.
Since most of the wall was blocked by buildings which were in contemporary use, the wall in its entirety could not be exposed. Instead, a man-made tunnel was excavated along the entire length of the west wall, underneath these buildings. Care was taken to insure structural support of the buildings above. It should be stressed that throughout all the work in this project, the tunnel was excavated outside of the Temple Mount itself. Needless to say, the tunnel was never in the vicinity of the mosques on the Temple Mount.
The tunnel enabled exposure of a small, though continuous section of the wall (a total length of ca. 500 m.), revealing important facts regarding methods of construction, the dating of various activities in the vicinity of the Temple Mount, not to mention various archaeological finds along the way. In effect, this project offered a manner to procure archaeological information which would have been impossible to attain through other methods. Noteworthy were finds from the Herodian period (streets, monumental masonry), sections of reconstruction of the Western Wall dated most probably to the Umayyad period and various structures dating to the Ayyubid and Mamluke periods constructed to support buildings in the vicinity of the Temple Mount. Though in fact various explorers had reached some of the remains that had been exposed in the tunnel, none had achieved quite such a comprehensive and robust picture as attained in the present project.
At the very northern portion of the Western Wall, an additional find was uncovered. This was the remains of a water channel which originally supplied water to the Temple Mount, though it was canceled out by the Herodian building. The exact source of the channel is unknown, though it passes through an underground pool known as the "Stroutioun Pool". The water channel was tentatively dated to the Hasmonean period (2nd-1st cent. BCE), and was dubbed the "Hasmonean Channel". The channel had already been reported in the 19th cent. CE by the British explorer Warren.
The current northern exit was made by tunneling in the bedrock next to the Stroutioun Pool, exiting on the Via Dolorosa, a public street. Needless to say, this tunneling as well was not conducted under or on the Temple Mount itself, and it is situated some 200-300 meters away from the Mosques on the Temple Mount. In other words, there was and is no archaeological or structural damage to the various historic Islamic edifices on or around the Temple Mount.
In summary, the Western Wall tunnels project has been an important avenue for exposing information relating to numerous periods in the history of the city of Jerusalem, information which otherwise would be near-impossible to attain. Close attention was paid throughout the entire project (in conjunction with a team of engineers, architects and conservators) that these activities would not damage buildings above and in the immediate vicinity of the tunnels. It should be stressed that none of these activities were under the Temple Mount itself and they did not in any manner endanger the various religious, historical and archaeological edifices on the Temple Mount.
Sources: Israeli Foreign Ministry