This mosque was a Catholic cathedral, and was built several times due to the collapse, and in the last restoration process it was built on a roof five times larger than before; Today it is a UNESCO World Heritage Site. The Katchaoua Mosque is characterized by its distinctive architectural character that combines ancient Roman, Byzantine and Arabic architecture, in addition to the Islamic decorations and inscriptions that adorn its walls. It is a really wonderful mosque, a must visit when coming to the city.