Corcovado National Park — The remotest and wildest of Costa Rica's parks, on the Osa Peninsula. Primary rainforest, jaguars, tapirs, all four monkey species, scarlet macaws. The Sirena ranger station is the destination; get there by hiking the coastal trail or flying in on a light aircraft. Book permits and a licensed guide well in advance.
Arenal Volcano — The classic Costa Rica experience. The perfectly conical stratovolcano towers above the town of La Fortuna and the Arenal lake. Hot springs around the base (Tabacón, Baldi, and several cheaper alternatives) make an obvious end to a hiking day. Arenal was continuously active from 1968 until 2010 and now sleeps, but the landscape is extraordinary.
Monteverde Cloud Forest — The road is rough and the weather is reliably misty, but Monteverde is worth it. Hanging bridges through the canopy, guided night walks, and the chance of seeing a resplendent quetzal (best February–April) are the draws. The area has multiple reserves; the Children's Eternal Rainforest is the largest private reserve in the country.
Manuel Antonio National Park — Small, crowded, and genuinely lovely. White sand beaches, reliable wildlife (squirrel monkeys, sloths, coatis), short forest trails, and calm swimming. Come early morning on a weekday to beat the crowds.
Chirripó — Costa Rica's highest peak at 3,821 meters. The two-day climb through paramo and cloud forest is one of the best hikes in Central America. Limited permits; book months ahead through SINAC.
Tortuguero — Only accessible by boat or small plane, this village on the Caribbean coast sits between the jungle canals and the turtle-nesting beach. Green sea turtles nest here July–October in enormous numbers. The canal boat trips are superb for wildlife: caimans, river otters, herons, monkeys, and manatees occasionally.
Puerto Viejo de Talamanca — The Caribbean's most characterful beach town. Afro-Caribbean culture, excellent food, good surf at Salsa Brava, and access to Cahuita National Park and the Gandoca-Manzanillo refuge.
Chirripo and San Gerardo de Rivas — The base town for the Chirripó climb. Very small, very quiet, with good trail access and a handful of simple guesthouses.
Whitewater rafting — The Río Pacuare between Turrialba and the Caribbean lowlands is rated among the best rafting rivers in the world. Class III–IV rapids through primary forest gorge; multi-day trips camping on the riverbank. Ríos Tropicales and Exploradores Outdoors are established operators.
Cahuita — A low-key Caribbean village with a coral reef just offshore, a good national park, and a distinctly unhurried pace. One of the better spots to slow down for a few days.