Cala Sant Esteva, 70, 07720 Cala de Sant Esteve, Illes Balears, Spain
Fort MarlboroughMinorca’s deep, protected harbor in the Mediterranean made it a valuable prize for invading forces throughout the island's history. In the early 1700s the British took control, quickly building Fort Marlborough to defend their position. The heptagonal (seven-sided) fort is small but well concealed—it's mostly underground, and entered through a tunnel. Tours take about 45 minutes, and include reenactments with special effects, videos and costumed soldiers.