Built by the Spanish in the early 16th century, the Ozama Fortress is the first permanent military structure in the Americas, marking the beginning of Spanish colonization. Set at the back of sprawling, walled grounds, the fortress was built to resemble a medieval castle and is marked by a 69-feet tall central tower. The tower’s winding, spiral staircase leads to a lookout platform with impressive views over the Ozama River, and Santo Domingo’s port. Also visible are the original cannons facing the river to protect the city’s entrance from pirates and invaders. Construction of the fortress lasted from 1502 to 1508, led by then-Santo Domingo governor Fray Nicolás de Ovando. Admire the fort’s original coral stone material and medieval appearance, but also explore its interior tunnels and dungeons where prisoners, including Christopher Columbus, were once held captive.