In close distance to the History Museum of Catalonia resides the Clock Tower. This is an example of some of the ancient constructions in the neighborhood. It was constructed in 1772 within the Fishermen's Wharf and worked as the lighthouse port up until the mid 19th century. When the port was modernized, the use for the lighthouse became obsolete. To maintain its base, the tower was transformed into a clock in the mid 19th century. This clock tower was one of the materials used by scientist Pierre Méchain as he measured the length of the meridian arc between Barcelona and Dunkirk in 1791, which led to the creation of the decimal metric system.