Nizwa was formerly a major center of Islamic education, and two of the oldest mosques in the world have survived since the early seventh century. One of them is the Citadel Mosque, which is located in the heart of Nizwa city opposite the market and the city fortress, and forms part of a group of magnificent buildings in the city center. The Citadel is one of the largest mosques in the Sultanate of Oman. It has a wonderful architecture with an authentic Arab character, and includes a large dome and minaret.