This sprawling city park ("Eastern Lookout Park" in English) lies across the Río Ozama from the Zona Colonial. The park's most visible feature is a monument to Christopher Columbus.
The park is riddled with caves -- really, limestone sinkholes -- created eons ago. The most famous and most explored of these is Los Tres Ojos (the Three Eyes), which can be reached by taking a long staircase carved into the side of this cave. Here, three lagoons are set in these scenic caverns, studded with lots of stalactites and stalagmites. One lagoon is 12m (39 ft.) deep, another 6m (20 ft.) deep. A third lagoon -- known as "Ladies Bath" -- is only 1.5m (5 ft.) deep. A Dominican Tarzan will sometimes dive off the walls of the cavern into the deepest lagoon. You can explore the caverns on walkways. Admission is RD$50, and visits are possible daily from 9am to 5pm.
Popular with joggers and cyclists, the park is also peopled with some of the most aggressive souvenir hawkers in the Dominican Republic. To see the park's natural attractions, anticipate lots of hassle to buy postcards, jewelry, or whatever.