It was built in 1772 and turned into a clock in 1904. Its initial function was the lighthouse that marked the entrance to the port. It was located on a bastion that also housed the
captaincy and the expedition of passages.
The growth of the docks and the construction of the Montjuļc lighthouse made obsolete the old lighthouse, which in 1904 was saved from demolition turning into a clock.
It also has the honor of being a geodesic point where Pierre F. Mechain took the last steps that led to the birth of the metric system.