The coastal town of Al Zubarah was surrounded by two walls, several kilometres of which were excavated during archaeological research. The outer wall, visible in this photograph, is built from rough coral limestone assembled with lime mortar. Its construction corresponds to the main development phase of the city, at the end of the 18th century. At that time, it was punctuated by twenty-two circular towers integrated into the construction of the houses. The later, lower inner wall with eleven towers covered the route of former streets. Aerial surveys suggest that Al Zubarah was part of a larger complex of installations and fortifications that extended along the northern coast of Qatar.