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 imposing 16th-century walls that surrounded the city are still largely intact, and provide a stunning backdrop to the whole city, especially along the seafront. The ramparts, called bastioni, house numerous restaurants, bars, cafes and shops, which are great for a drink at sunset in the evening breeze.

Through guided tours or individually, visitors can stroll through this imposing campus and explore its 500-year history. On-site landmarks include the Hunterian Museum, Art Gallery and the Zoology Museum — or why not just soak up vibes at the students' favourite cafés and restaurants.