Image by Jacqui de Klerk Lonely Planet
The Old Town is surrounded by Las Murallas, the thick walls built to protect it. Construction was begun toward the end of the 16th century after the attack by Francis Drake; until that time, Cartagena was almost completely unprotected. The project took two centuries to complete, due to repeated storm damage and pirate attacks. It's possible to walk along large stretches of these magnificent structures, with wonderful sea views and a cooling breeze from the the northern and western sides.
Las Murallas are an outstanding piece of military engineering, and are remarkably well preserved, except for a part of the walls facing La Matuna, which were unfortunately demolished by 'progressive' city authorities in the mid-20th century.