A feat of Spanish colonial military architecture, the Castillo San Felipe de Barajas is one of Cartagena's most prized attractions. The fortress, whose construction finished in the late 18th century, was never seized – and not for a lack of attempted forays. Part of its sophisticated system of underground tunnels is open to the public; a guided tour (audio guides available) is highly recommended.

Enclosed within a protective wall reaching up to 20 m 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.

The buzzing Bairro Getsemani is, perhaps, Cartagena's most attractive neighbourhood, for both its well-preserved colonial architecture and vivid street life. Known as the nightlife hot spot of Cartagena, Getsemani stays up until late at night, with locals and visitors mingling in and around Plaza de la Trinidad over drinks and street food.

Enjoy a stroll through the stunning sculptures and the thousands of amazing cactuses of this botanical garden. Alternatively, rent a bike and let yourself be amazed by the fascinating mix of central Mexican indigenous culture and cactus plants from around the world.