The castillo is the greatest fortress ever built by the Spaniards in any of their colonies. It still dominates an entire section of Cartagena's cityscape today, and should definitely be your first choice of fortresses to visit. The original fort was commissioned in 1630 and was quite small. Construction began in 1657 on top of the 40m-high San Lázaro hill. In 1762 an extensive enlargement was undertaken, which resulted in the entire hill being covered over with this powerful bastion.
It was truly impregnable and was never taken, despite numerous attempts to storm it. A complex system of tunnels connected strategic points of the fortress to distribute provisions and to facilitate evacuation. The tunnels were constructed in such a way that any noise reverberated all the way along them, making it possible to hear the slightest sound of the approaching enemy's feet, and also making it easy for internal communication.
Some of the tunnels are lit and are open to visitors – an eerie walk not to be missed. Take an audio tour (COP$10,000 in English) if you want to learn more about the curious inventions of Antonio de Arévalo, the military engineer who directed the construction of the fortress.
The fortress is a short walk from Getsemaní, but if you're in a hurry a taxi costs COP$6000. Entrance is free the last Sunday of every month between February and November.
