The walls of Cartagena are extraordinary feats of engineering. In some places they are 17 metres high and 20 metres thick. They took over 200 years to build, and were designed to protect the city from attacks from the sea. Today those same walls are a favourite place for an evening stroll, with views over the rooftops and out to the Caribbean.
Walking inside the walled city is like stepping into a painting. The houses are painted in bright yellows, pinks, blues and oranges. Wooden balconies on the upper floors are covered in cascading bougainvillaea flowers. The streets are made of stone and too narrow for most cars - horses and bicycles are more common.
The city is full of plazas - open squares where people gather in the evenings. The biggest is the Plaza de Bolívar, with a garden and a fountain in the middle. Street vendors sell fresh fruit juice, coconut sweets and fried food from carts and baskets balanced on their heads.
Outside the walls lies the modern city - a busy port, big hotels and wide avenues. But most visitors spend their time in the old town, where the streets tell stories in every stone. Cartagena's old city is one of the best preserved colonial city centres anywhere in the Americas.