The Great Mosque in Kairouan is the most important of all in Tunisia. It is the oldest Muslim place of worship in Africa and is commonly regarded as the fourth holiest site in Islam after Mecca, Medina and Jerusalem. It was originally built by Oqba ibn Nafi, the Arab commander who founded Kairouan in AD 672. The mosque covers a mammoth area 135 m long by 80 m wide with a vast inner courtyard surrounded on three sides by double-aisled colonnades of antique columns. Non-Muslims are not allowed to enter the prayer hall but the doors are often kept open so you can have a peek inside.