Corcovado is the rainforest National Geographic called the most biologically intense place on Earth, and the numbers hold up. The Osa Peninsula it sits on carries roughly 2.5 percent of all life on the planet in less than a thousandth of its surface. Across 424 square kilometres of roadless lowland jungle live more than 500 species of tree — more than are native to all of Europe — along with some 140 mammals and 400 birds. All four of Costa Rica's monkeys move through the canopy here. The park guards the country's largest population of scarlet macaws, along with jaguars, pumas and endangered Baird's tapirs, the largest land animal in Central America. It survived the chainsaw largely because it was so hard to reach: no road runs to its heart, and the forest meets the Pacific along long black-sand beaches with nobody on them.
Nature still sets the terms here. Trekking the muddy trails between the coastal ranger stations, you hear scarlet macaws before you see them — pairs screeching overhead in flashes of red and blue. Spider monkeys crash through the branches and tapir tracks press into the riverbank. Most visitors reach the interior Sirena station by boat, riding out from the Sierpe River or Drake Bay and landing straight onto a surf-washed beach. You wake there to a wall of birdsong at first light, in thick dripping heat, with fresh animal tracks written across the sand. This is one of the last lowland rainforests never cleared, farmed or logged, so the forest you walk through is working exactly as it always has. That remoteness is now guarded by rule as well as distance: since 2014 every visitor must enter with a licensed guide and a permit booked ahead. Rangers still patrol against the illegal gold miners who work its far corners.