Badajoz bastioned enclosure

The bastioned system of the Spanish city of Badajoz consists of a military fortification formed by a set of defensive walls, city gates, bridges, forts, towers, bastions, hornworks, moats, tunnels, and ravelins, among other defensive elements. It was built during the 17th and 18th centuries, following the defensive construction theories popularized by the French military engineer Marquis de Vauban, as an extension of a previous defensive enclosure that protected the Portugal–Spain border city.

Source: Wikipedia — Badajoz bastioned enclosure (CC BY-SA 4.0)