El Yunque National Forest

The only tropical rainforest in the U.S. National Forest System, and the simplest rainforest trip for most American readers: no passport needed and an easy day trip from San Juan. At nearly 29,000 acres it is one of the smallest national forests, yet one of the most biologically diverse, and it climbs from lowland forest into misty peaks. Entry to the main recreation corridor on Route 191 is free and needs no reservation, with gates open from 8 a.m. to 5 p.m. Parking is limited and the Forest Service still manages visitor numbers while recovery construction continues, so arrive early and check trail closures first. Stay nearby overnight to hear the island's tiny coquí frogs fill the dark with their calls.