Cartagena Fortress

Castillo San Felipe de Barajas is a fortress/castle in the city of Cartagena.  The castillo is the greatest fort ever built by the Spaniards of any of their colonies.  Construction began in 1657 on top of San Lazaro hill.  The tunnels were said to provide a great form communication, in which messages could be relayed to one another, and approaching intruders could be heard.