Regions to know
To frame your trip by what you have time for and what you're after.
Central Valley & San José
San José, Poás, Irazú, Doka coffee tour
Where you land (SJO airport) and not much else. Poás volcano is 1hr north, Doka coffee is on the way. San José city has the Pre-Columbian Gold Museum but isn't a destination — most travelers leave for Arenal or the coast within hours.
Arenal & northern lowlands
Arenal Volcano, La Fortuna, Caño Negro wetlands
The activity capital — volcano + hot springs + waterfalls + zip-lines + hanging bridges + rafting. La Fortuna town has the densest concentration. 3 days minimum.
Monteverde & cloud forests
Monteverde Cloud Forest, Santa Elena, hummingbirds
High-altitude misty forests, cooler temperatures (15–22°C), best birding. The road from Arenal is famously rough (3–4 hours of dirt road); some take the boat-jeep-boat shortcut. 2 days is right.
Pacific Coast (Manuel Antonio, Nicoya)
Manuel Antonio, Jacó, Tamarindo, Nosara, Santa Teresa
The beach circuit. Manuel Antonio for the postcard small park + beach. Nicoya peninsula for surf and Blue-Zone-yoga vibe. Liberia airport (LIR) is the gateway for Guanacaste; SJO works for Manuel Antonio.
Caribbean coast (Limón)
Tortuguero, Cahuita, Puerto Viejo, Manzanillo
Afro-Caribbean culture, reggae, slower pace, jerk chicken and rondón stew. Tortuguero north for turtle nesting; Cahuita and Puerto Viejo south for beach-town reggae vibe. Different country, basically.
Osa Peninsula (Corcovado)
Corcovado, Drake Bay, Puerto Jiménez, Cocos Island offshore
The wildest part of the country — primary rainforest, all four monkey species, scarlet macaws, the elusive jaguar. Hard to reach (small plane from SJO recommended), expensive lodges, mandatory guides in Corcovado. Worth the effort for a second trip.