Introduction to the city wall: Avila's city wall (Muralla) was built in the 12th century and is the oldest existing medieval city wall in Europe. The city wall is nearly quadrangular in shape, with a total length of 2550 meters, a width of 3 meters, and a height of about 12 meters. There is a tower every 25 meters, with a total of 90 towers, 9 gates, 88 circular bunkers and 2500 battlements. It has a unique shape and majestic architecture.