Castles, often built on hills with extremely steep slopes, or on sea cliffs overlooking stretches of water, were difficult to conquer. Construction techniques and geomorphology of the area were a key factor in making castles impregnable to sieges of military troops or bands of pirates or robbers. Today, the same characteristics make them difficult to survey. In fact, there are huge difficulties in surveying fortified structures on the top of hills or on the edge of a precipice.
Cartagena de Indias, one of the main Spanish commercial ports in the Caribbean Sea, was strategically built on a system of islands and peninsulas that formed a lacustrine system along the coast of Tierra Firme, known today as Colombia. For several centuries, Cartagena fortifications have been at the fore-front of Spanish military technologies. This site became the scene of action of the main military engineers at the service of the Spanish crown. In 1586 Battista Antonelli received from King Philipe II the task to design this monumental defensive system.