The Baluarte de San Carlos is one of the eight bastions of the original hexagonal wall system and houses the Museo de la Ciudad (City Museum). The pentagon-shaped fort sits at the corner of the walls nearest the modern centre and is among the most accessible of the bastions.
The City Museum traces Campeche's history from pre-Columbian times through the colonial period and the 19th century, with a particular focus on the pirate attacks that shaped the city's physical form. Scale models of the city at various historical periods help visualise how the defensive system worked. The dungeon tunnels beneath the fort are open to visitors and have a suitably atmospheric quality — cool, dark, and evocative of what happened in them.