Corcovado is a roadless rainforest on the Osa Peninsula of southern Costa Rica, never logged, that National Geographic called the most biologically intense place on Earth — and most people arrive on its beach. An open boat runs out from Drake Bay or down the Sierpe River and drives straight up onto the sand, because there is no road into the middle of the park and nothing for you to drive to. The forest begins where the sand stops. Giant trees stand over a long black shore with the Pacific breaking on it, and the coastal trail to the Sirena ranger station follows that line, wading river mouths and crossing one empty bay after another. However inviting those river mouths look, they belong to bull sharks and crocodiles rather than swimmers. Everyone walks with a licensed guide, because the park allows nothing else.
What the guide mostly reads is the ground. Fresh prints in the sand and the mud turn the walk into a running tally of who came through in the night, and the interior trails around Sirena are the best ground for it: tapir tracks, peccary wallows, the occasional cat. Baird's tapir, the largest land animal in Central America, lives here in one of its densest populations anywhere and is met on dawn and dusk walks, wading the shallows. Jaguars and pumas are here too, and you will almost certainly not see them. Over the almond trees along the shore, scarlet macaws cross in loud pairs of red, blue and yellow. This park guards the largest population in Costa Rica, so they come thick and fast, and all four of the country's monkeys move through the canopy behind them. Four kinds of sea turtle haul out onto the same black sand to lay their eggs, the leatherback among them, up to two metres long. Gold moves in these rivers, and prospectors were panning the creeks long before any park existed. A night at Sirena wakes you to surf and birdsong, and puts you on that beach at first light, reading what crossed it while you slept.