Cartagena, together with La Habana and San Juan de Puerto Rico, was one of the three most important ports in the West Indies. It is an outstanding example of the military architecture of the 16th-18th centuries - the most extensive in the New World and one of the most complete.
On 1 June 1533 the Madrileño Don Pedro de Heredia founded Cartagena de Indias on a tiny coastal archipelago in the Caribbean. Located in the Gulf of Darien, 100 km west of the mouth of the Rio Magdalena, Cartagena used the advantages both of its position and of its site: a narrow band of land cut off from the continent by a succession of bays offering good anchorage and by narrow channels which constituted an excellent natural defence. A century later, this was where all the stolen treasures from the Indians of New Granada were stored before being moved to Spain. Cartagena grew rich on palaces, gardens, convents and churches, adopting the Catalan and Andalusian styles.
In 1586, the most famous military engineer of the Crown of Spain, Bautista Antonelli, was charged with the fortification of the city. His work, finally completed in the 17th century, made Cartagena an impregnable stronghold, which successfully resisted the attacks of Baron Pontis until 1697. In the 18th century, new additions gave the fortified ensemble its present spaciousness. The initial system of fortification included only the urban enclosure, the bastioned harbour of San Matias at the entry to the pass of Bocagrande, and the tower of San Felipe del Boqueron which controlled the Bahia de las Animas. Little by little, all of the passes were dominated by forts: San Luis, San José and San Fernando in Bocachica, San Rafael and Santa Barbara in Pochachica (the south-west pass); Santa Cruz, San Juan de Manzanillo and San Sebasi de Pastellilo around the interior Bahia; San Felipe de Barajas, on the rocky crag which dominated the city to the east and protected the access to the isthmus of Cebrero. The fortifications of San Felipe de Barajas protected Cartagena during numerous sieges, giving the city its unconquerable character and reputation. They are described as the masterpiece of Spanish military engineering in America.
Within the shelter of the formidable defences, the city continued to grow. The plan, characteristic of colonial foundations of the 16th century, illustrates a rigorous zoning system, divided into three quarters corresponding to the major social categories: San Pedro, San Diego and Gethsemani.
The old city conserves all the enchantment of the colonial period, with its narrow streets flanked by beautiful inner doors and projecting balconies. Entry by the Puerta del Reloj, the main entrance of the walled enclosure, gives access to the Plaza de los Coches, where long ago the slave market was held. The quarter of San Pedro, where the nobles and the notables resided, still preserves monuments of high quality such as the cathedral (1575-1612), the church and convent of San Pedro Claver, the church of Santo Domingo, and the building that once was the monastery of San Diego. In the Palace of the Inquisition, a beautiful structure with a magnificent inner door in Baroque style, the Court of the Holy Office carried out its functions, judging witchcraft and heretical cases. Today it houses a historical and archaeological museum; the Palace of the Government, and the home of Marquia de Valdehoyos.
The quarter of San Diego, to the north-east, was where the merchants and middle-class craftsmen resided; to the south-west, on a small island which slowly became attached to the mainland, was Gethsemani, the popular quarter. In the north sector of the walled city is the Plaza de los Coches, under whose arches ammunition and military equipments were stored and where troops were stationed during the colonial period. Outside the perimeters of the walls the Monasterio de la Popa, built on the summit of a hill that dominates the whole city.