The Ottoman Citadel of Borj al-Kabir, also known as the Kasbah of Mahdia, is located in the center of the city of Mahdia. It is a fortress erected at the end of the sixteenth century on the site of an old Fatimid palace. It is considered one of the most beautiful samples of Ottoman military architecture. Its scattered architecture and the absence of a minaret make it more like a fortress. From being a religious building, the building was founded on a quadrangular plan, is surrounded by a strong wall, and has a single entrance that gives access through a vaulted and folded corridor to a courtyard that gives the rooms an open vault. This imposing tower from the sixteenth century was the Fatimid watchtower. It hosts a silk market and traditional women’s jewelry every Friday, where embroiders come from the city or the surrounding areas to present their shimmering work, and when you climb to the top of the tower, you can enjoy a very beautiful view that dominates the entire city.