Quba Mosque

The Quba Mosque is a mosque located in Medina, in the Hejaz region of Saudi Arabia, built in the lifetime of the Islamic prophet Muhammad in the 7th century C.E. It is thought to be the first mosque in the world, built on the first day of Muhammad's emigration to Medina. Its first stone is said to have been laid by the prophet, and the structure completed by his companions. The mosque was subsequently modified across the centuries until the 1980s, when it was completely replaced by a new building that stands today.

Source: Wikipedia