Which national parks should I visit?

This really depends on a variety of factors such as what species of wildlife and habitats you would like to see, the time of the year you are visiting, if you are willing to travel to remote locations, your budget, and what else you would like to do while you in Costa Rica.  

Top 10 Reserves & National Parks in Costa Rica and Why You Would Visit Them

Arenal Volcano National Park: Arenal Volcano is the most popular attraction in Costa Rica.  Visitors come for hot springs, volcano, adventure, wildlife, and jungle.

Manuel Antonio National Park: Manuel Antonio offers an immense amount of wildlife for such a small area.  There are also beautiful beaches, jungle and plenty of adventure activities.

Monteverde Cloud Forest Reserve: The Monteverde Reserve offers world-class highland birdwatching opportunities. Note that this is a private reserve and not a national park. The Curi Cancha Reserve is in the same area and has fewer visitors and often, better odds of spotting wildlife.

Tortuguero National Park: Tortuguero is one of the most remote national parks in Costa Rica, protecting numerous species of wildlife within the jungle and canals as well as several species of sea turtles.

Corcovado National Park: Corcovado is the most remote national park in Costa Rica and one of the most biologically diverse places in the world.

Rincon de la Vieja National Park: Rincon de la Vieja is one of Costa Rica's active volcanoes.  Visitors to the Las Pailas section can get up close and personal with hot springs, fumaroles and natural steam vents.

Cahuita National Park: Cahuita offers excellent snorkeling at certain times of the year and excellent wildlife observation in the jungle trails.

Palo Verde National Park: Palo Verde is best visited by riverboat to see white faced monkeys, giant crocodiles, iguanas, and waterfowl.

Cano Negro Wildlife Refuge: Cano Negro is also best visited by boat.  It's a nice day trip from the Arenal area to see caimans, monkeys, waterfowl and other exotic wildlife.

Marino Ballena National Park: This south Pacific marine park protects whales, dolphins, sea turtles, and more.