The Omar Mosque:

When Caliph Omar Ibn al-Khattab conquered Jerusalem in 638, he was shown the great Church of the Holy Sepulcher and offered a place to pray in it, but he refused. He knew that if he prayed in the church, it would lead to the Church’s transformation into a mosque. He instead prayed on the steps outside, allowing the church to remain a Christian holy place. The Omar Mosque was built near the site of these events in 1193.