2-370-047 - Samuel Magal/Sites & Photos/Heritage Images

The walls of Avila, Spain, 2007. Avila's crenellated city walls are the best preserved in Spain. Built in the 11th and 12th century under Raymond of Burgundy, son-in-law of Alfonso VI, today they are 2.5 km long, 40 feet high and 10 feet thick, with approximately 2,500 battlements, 88 towers, 6 gates and 3 wicket gates. The fortification is the only instance of its kind of Medieval European architecture. The friezes and brick borders tell us that Mudejar and Moorish master builders also played a part in the walls' construction. Avila was declared a World Heritage Site by UNESCO in 1985.