Numantia was an ancient Celtiberian settlement. It was an Iron Age hill fort, which controlled a crossing of the river Duero.
Numantia is famous for its role in the Celtiberian Wars. In the year 153 BC Numantia experienced its first serious conflict with Rome. After 20 years of hostilities, in the year 133 BC the Roman Senate gave Scipio Aemilianus Africanus the task of destroying Numantia. He laid siege to the city, erecting a nine kilometre fence supported by towers, moats, impaling rods and so on. After 13 months of siege, the Numantians decided to burn the city and die free rather than live and be slaves.
After the destruction, there are remains of occupation in the 1st century BC, with a regular street plan but without great public buildings. Its decay starts in the 3rd century, but with Roman remains still from the 4th century. Later remains from the 6th century hint of a Visigoth occupation.
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.