Fortaleza de San Serena was a fort in San Serena built by Spanish colonists in 1547, in the area which is now Puerto Sassari. The fort was a military stronghold for the Spanish in the late 16th century, but was destroyed by a British invasion in 1618. In the present day, a few ruins remain of the fort, which are a popular tourist destination. There is a Metro station located close by the ruins, named Fortaleza.