Charles V's Castle is located in the old part of Crotone. Built in 840 to defend the city from Saracens, it was modified in 1541 by Charles V. It has polygonal shape, with two towers: a more massive called "Helper Tower", and another called "Commander Tower". The building began as a fortress on ancient Greek acropolis; over the years, there have been several interventions, up to the current configuration, commissioned by Viceroy Don Pedro of Toledo to Gian Giacomo of Acaya. The entrance was a semi-mobile bridge in masonry and wood; the main door was inserted in a tower of a truncated pyramid. The excavations in the ditch, conducted by Superintendent in 2011, have brought to light the base of large square tower called "Crank", with which it was raised the bridge. They were integral part of defense complex also St. James's Bastion, which dominated the harbor and marina and served as a shelter to the troops; and St. Catherine's Bastion. Helper Tower was used as dwelling of the officers; Marchesana Tower, circular base armed with four guns, stood inside Castle and was intended to prison for convicts who built the port (destroyed by the earthquake of 1862). Under Marchesana there was a smaller tower, with numerous loopholes for riflemen. Within the walls of Castle there were St. Dionisio's Church (1601), New Church and St. Carlo's Churh (1859), the lodging of Castle, the stores of artillery, a barracks for women and a prison, known as "The Serpent". Today, Helper Tower houses Civic Museum.