Dating back to the 17th century, this fort in pentagonal shape is the seat of the city museum, exhibiting various historic artifacts.
Wikipedia (Spanish) http://es.wikipedia.org/wiki/Baluarte_de_San_Carlos
More information http://www.campeche.travel/baluarte-de-san-carlos/
Address 329 Calle 8, Campeche 24000, Mexico
Coordinates 19°50'40.496" N -90°32'26.071" E