The Sqifa al-Kahla, also known as Bab Zuweila, is a huge fortified gate dating back to the 10th century, restored in the 16th century, and still one of the main access points to the historic center of Mahdia, and one of the rare monuments of the ancient city walls. It is located in the center of the old castle. The Sqifa al-Kahla, which is the only remnant of the ancient walls, was incorporated into the system of walls rebuilt by the Turks at the end of the sixteenth century, and was the main tower of the second line of defense to prevent access to the city by land. The building consists of two parts; An 18 meter long fortress restored at the end of the 19th century and an arched vestibule that was used as a defense and as a trade passage once a week during the market. Today, the famous penthouse hosts the city's weekly market.