The wilderness just behind the Fuerte San Lorenzo is part of Parque Nacional San Lorenzo, a 23,843-acre (9,653-hectare) protected area that includes rain forest, wetlands, rivers, and coastline. For decades this was the U.S. Army's jungle training area, where tens of thousands of troops trained for warfare in the tropics. The army used parts of the park as a bombing range, and there may still be unexploded ordnance in its interior, though far from the roads and fortress.
Today the park is the haunt of bird-watchers, who hope to focus their binoculars on some of the more than 400 bird species. Mammalian residents include spider monkey, armadillo, tamarin, and coati mundi. The lush forest here gets nearly twice as much rain as Panama City, and it doesn't lose as much of its foliage during the dry season. Most of that rain falls at night, so mornings are often sunny, even during the rainy season.
The most famous bird-watching area in Parque Nacional San Lorenzo is the Achiote Road (Camino a Achiote), which is about 25 km (15 mi) south of the fort. To reach it, turn left after crossing the locks and drive 15 km (9 mi) south. Members of the Panama Audubon Society once counted 340 bird species in one day on the Achiote Road during their Christmas bird count. The community of Achiote, about 4 km (2½ mi) northwest of the park on the Achiote Road, has trained birding guides and a visitor center with rustic accommodations.