The Tower of Hercules in La Coruna was built by the Romans as a lighthouse in the 2nd century A.D. The 55 m Tower sits on a 57 m hill. The first 34 m of the Tower date back to Roman times; the rest of the Tower was added during a renovation in 1791. The lighthouse is still working, and its light can be seen from 35 km at sea. The Tower is the best- preserved Greco-Roman structure of its kind and is the oldest functioning lighthouse in the world.