Wikipedia: The Ummayad Mosque, also known as the Grand Mosque of Damascus (Arabic: جامع بني أمية الكبير, transl. Ğām' Banī 'Umayyah al-Kabīr), is one of the largest and oldest mosques in the world. Located in one of the holiest sites in the old city of Damascus, it is of great architectural importance.
The mosque holds a shrine which is said to contain the head of John the Baptist (Yahya), honored as a prophet by Muslims and Christians alike. The head was supposedly found during the excavations for the building of the mosque. There are also many important landmarks within the mosque for the Shī‘ah, among them is the place where the head of Husayn (the grandson of Muhammad) was kept on display by Yazīd I. There is also the tomb of Saladin, which stands in a small garden adjoining the north wall of the mosque.
In 2001 Pope John Paul II visited the mosque, primarily to visit the relics of John the Baptist. It was the first time a pope paid a visit to a mosque