Saudi Arabia is a desert nation that covers most of the Arabian Peninsula, with coastlines along the Red Sea and the Persian Gulf. It is considered the birthplace of Islam and has the two most important mosques in the religion. The first is Masjid al-Haram in Mecca, where millions of Muslims gather every year for the Hajj pilgrimage. The second is Masjid an-Nabawi in Medina, which is where the prophet Muhammad is buried. The capital city, Riyadh, is a modern city with many tall buildings.