The Western Wall Tunnel is a tunnel exposing the Western Wall from where the traditional, open-air prayer site ends and up to the Wall's northern end. Most of the tunnel is in continuation of the open-air Western Wall and is located under buildings of the Muslim Quarter of the Old City of Jerusalem. While the open-air portion of the Western Wall is approximately (200 ft) long, the majority of its original length of (1,601 ft) is hidden underground. The tunnel allows access to the remainder of the Wall in a northerly direction.    www.Maranathatours.com

The biggest stone in the Western Wall, often called the Western Stone, is also revealed within the tunnel, and ranks as one of the heaviest objects ever lifted by human beings without powered machinery. The stone has a length of (45 ft), height of (9.8 ft), and an estimated width of between (11-15 ft) ; estimates place its weight at 570 short tons (520 metric tons).

In 19 BCE, King Herod undertook a project to double the area of the Temple Mount in Jerusalem by incorporating part of the hill on the Northwest. In order to do so, four retaining walls were constructed, and the Temple Mount was expanded on top of them. These retaining walls remained standing, along with the platform itself, after the Temple was destroyed by the Romans in 70 CE.

Since then much of the area next to the walls became covered and built upon. Part of the Western Wall remained exposed after the destruction of the Temple. Since it was the closest area to the Temple’s Holy of Holies that remained accessible, it became a place of Jewish prayer for millennia.

The excavations were difficult to conduct, as the tunnels ran below residential neighborhoods constructed on top of ancient structures from the Second Temple Period. The excavations were conducted with the supervision of scientific and rabbinic experts. This was to ensure both the stability of the structures above and to prevent damaging the historic artifacts.

Beyond the northern end of the Western Wall, remains were found of a water channel that originally supplied water to the Temple Mount. The exact source of the channel is unknown, though it passes through an underground pool known as the "Struthion Pool". The water channel was dated to the Hasmonean period and was accordingly dubbed the "Hasmonean Channel".

In 1996, however, Benjamin Netanyahu authorized the creation of an exit leading to the Via Dolorosa, underneath the Ummariya madrasah. One side is visible from the western wall tunnels, and the other area is accessible from the Convent of the Sisters of Zion. Since then, it has been possible for large numbers of tourists to enter the tunnel's southern entrance near the Western Wall, walk the tunnel's length with a tour guide, and exit from the northern end.