What became of the 1980s efforts of a group of Swedish schoolchildren to save the rainforest? Only this enormous 220 sq km reserve – the largest private reserve in the country. It's mostly inaccessible to tourists, with the exception of the well-marked 3.5km Sendero Bajo del Tigre, which is actually a series of shorter trails. Make reservations in advance for the popular two-hour night hikes.
At the entrance there’s an education center for children and a fabulous vista over the reserve.
The Estación Biológica San Gerardo, reachable by a rather gnarly 2½-hour trail from Reserva Santa Elena, is managed by BEN and has dorm beds for researchers and students, but you may be able to stay overnight with prior arrangements.