Just an hour's boat trip away from Cartagena lie the magnificent Rosario Islands, which belong to Colombia's only underwater natural park (Rosario and San Bernardo Corals National Natural Park). Abundant marine wildlife (including over 50 species of corals) and some of Colombia's best beaches draw in many in search of relaxation and active pursuits such as snorkelling and diving. Isla Grande is best for kayaking through unique mangrove forests and seeing the phosphorescent plankton light up the waters of a brackish lake at night, while Playa Blanca is Cartagena's most spectacular white-sand beach (also reachable by land). It should be said that the company you choose to tour with has the potential to make or break the experience. Low cost tours can mean multiple intermediate stops en route to your destination, as well as unpleasant surprises such as no transfer back to your hotel. Try and choose a trusted company with consistently good reviews, or opt for a private tour. Mind that seas may be rough at certain times of the year, particularly in December and January, when tours on smaller boats may even become dangerous.

Enclosed within a protective wall reaching up to 20 metres in width, the Ciudad Amurallada (or Walled City) is Cartagena's old beating heart. Packed with well-preserved colonial buildings, it's a pleasure to stroll through; its streets of colourful low-rise merchant homes marked by iconic balconies are now mostly walked by either tourists or students who attend classes at the University of Cartagena during the day and linger for meals and nightlife after school is out. Cafes in Plaza Aduana and Plaza Santo Domingo teem with patrons, forging an incredibly jovial atmosphere; the districts of San Diego and El Centro are two not to be missed. There is plenty of food and shopping to be had, with a mixed bag of world-class restaurants and street food hawkers and the incredibly photogenic palenqueras — women dressed in vibrantly coloured clothing selling fruit in the streets — images of whom have become emblematic of Colombia as a travel destination.

This beautiful example of Spanish colonial architecture contains a small museum dedicated to the Spanish Inquisition's brutal persecution of heretics once carried out in these very chambers. Visitors can still see some of the torture devices used to extract confessions of heresy and witchcraft, along with some of the questions used in "witch" interrogations, which are still displayed on the museum wall. Needless to say, no prisoner could hope to be acquitted of their purported crimes against the Catholic Church, and most met their tragic end at the very guillotine still on display in the courtyard.