Komárno castle became the main supporting point of the defensive system constructed against the Turks, after they occupied Buda and Esztergom in the years 1541-1543. The fortress of Komárno is the one of the largest bastion fortifications in Central Europe. It was built in 1546-1557 to the grounds of the 13th century castle.
The city walls of Avila were built in the 11th century to protect the citizens from the Moors. They have been well maintained throughout the centuries and are now a major tourist attraction as well as a UNESCO World Heritage Site. Visitors can walk around about half of the length of the walls.
The layout of the city is an even quadrilateral with a perimeter of 2,516 m. Its walls, which consist in part of stones already used in earlier constructions, have an average thickness of 3 m. Access to the city is afforded by nine gates of different periods; twin 20 m high towers, linked by a semi-circular arch, flank the oldest ones, Puerta de San Vicente and Puerta del Alcázar.