Wonderfully preserved Cartagena is one of the country’s oldest settlements and without doubt one of South America's most impressive colonial cities. It features impressive fortifications with a series of seven forts protecting the sea approaches and almost impregnable city walls. The Castillo San Felipe de Barajas dating from 1639 was the largest Spanish fort built in the Americas. The historic centre is a maze of narrow old streets, arcaded plazas and grand colonial buildings, notable among them the baroque Palace of the Inquisition, the Gold Museum and the Cathedral, all around Plaza de Bolivar. There are several interesting monasteries and churches including Santisima Trinidad, San Francisco, Santo Domingo and San Agustin. From here you can also explore the coral reefs around the Islas del Rosario or take a mud bath near the El Totumo volcano.