The Murallas de Ávila are the best preserved and most complete medieval fortifications in Spain. The walls were built between the 11th and 14th centuries to control the entrance of merchandise and provisions, and to isolate the city from epidemics. The walls are made of coloured masonry of different sizes and cover an irregular rectangle of 77 acres with a perimeter of 8,255 ft. They have 88 semicircular towers, averaging 33 ft in height, and more than 2,300 battlements. The walls have nine gateways, including the two most famous, the San Vicente and the Alcázar, both on the eastern side. The walls also contain the remains of ancient Roman funerary steles, burial mounds, altars, cists, cupas, and millstones.