The Western Wall or Wailing Wall, known in Islam as the Buraq Wall, is an ancient limestone wall in the Old City of Jerusalem. It is a relatively small segment of a far longer ancient retaining wall, known also in its entirety as the "Western Wall". The wall was originally erected as part of the expansion of the Second Jewish Temple begun by Herod the Great, which resulted in the encasement of the natural, steep hill known to Jews and Christians as the Temple Mount, in a huge rectangular structure topped by a flat platform, thus creating more space for the Temple itself, its auxiliary buildings, and crowds of worshipers and visitors.

In one of several varying Muslim traditions, it is the site where the Islamic Prophet Muhammad tied his winged steed, al-Buraq, on his Isra and Mi'raj to Jerusalem before ascending to paradise, and constitutes the western border of al-Haram al-Sharif, the Noble Sanctuary of the Al-Aqsa Mosque.

The Western Wall's holiness in Judaism is a result of its proximity to the Temple Mount. Because of the Temple Mount entry restrictions, the Wall is the holiest place where Jews are permitted to pray, though the Foundation Stone, the most sacred site in the Jewish faith, lies behind it. 

- Wikipedia