The first walls of Astorga,from high-imperial age, gave way to another wall, more ambitious and still preserved nearly in full. Its construction happens at the same time as a moment of reorganization in the fourth century, which gave a new role to the city. The cessation of the mine exploitations turned it into a strong space of vigilance of the roads for the transit of agricultural produce intended for the northern armies .The Roman gate,adjacent to the Cathedral,is the best preserved example of this building stage.
The Roman walls were rebuilt by Bishop Nuño around 1242 and they underwent several repairs during the Middle Ages, which has handed us down their present elevation and the disappearance of their gates and wickets (gates of the King, the Sun, the Bishop and Iron).Their perimeter reached 2,100 metres surrounding the 27 hectares with trapezoid shape which comprise the historic city. They have about thirty semicircular round turrets with an average diameter of seven metres. Their grand aspect, linked to the collection of the Cathedral and the Bishop's Palace, forms one of the best known images of Astorga.