Fortaleza Ozama (Calle de las Damas, tel. 809/686-0222, 9:30 a.m.–6:30 p.m. Mon.–Sat., 9 a.m.–4 p.m. Sun., US$1) was built in 1502 and underwent many changes and alterations over the next two centuries. From its prime position on a steep hill overlooking the mouth of the Ozama River, the Spanish launched conquests to Jamaica, Cuba, South America, and Mexico. It served as the first line of defense against attackers with its huge cannons, some of which are still aiming ominously at the waters below. Until the 1970s it served many functions, including as a military post and a prison, until it was opened to the public.

Inside the walls of the fort, the looming Torre del Homenaje (Tower of Homage), evoking classic Spanish castle design, is the oldest portion of the fort and has walls two meters thick. A climb to the top, up the narrow stairwells, is rewarded with a 360-degree view of Santo Domingo. Also on-site is El Polvorín (The Powder House), which acted as the artillery and ammunition house.

Standing in the middle of the walled yard is a bronze statue of Gonzalo Fernández de Oviedo, a famous historical chronicler who was put in charge of the fort; he lived and died there. His room was on the second floor of the fort and was turned into a prison cell after his death.

Optional and informative tours are offered by the guards at the front gate of the fort for about US$4 per person and given in Spanish, English, and French.