Arenal Volcano
The most active volcano in the whole country situated to the north of the capitol of San Juan, home to caves, Lake Arenal, and the Tabacon Hot springs, fed by the volcano.
Though the country is filled with volcanoes, the Arenal Costa Rica is the most picturesque of them all. Daily there are at least five small explosions, and some can even be heard, the lava flows easily visible.
The Arenal Volcano has been constantly active, glowing in the night and sending lava flowing down towards the north. Lake Arenal is a great drive.  

Turtugeuro National Park
Tortuguero National Park, the breeding ground for the green sea turtle, is where the rivers spill out into the ocean. It has been one of the wettest areas in Costa Rica reaching the rainfall up to 6,000mm. There are many beaches but the coastal area is not suitable for swimming having rough, strong surf and currents. Sharks are common. Thousands of green and leatherback turtles nesting and laying eggs can be viewed on the beaches overnight.

Corcovado National Park
Corcovado National Park is on the Osa Peninsula in the South West of Costa Rica, established on 24 October 1975, widely considered the crown jewel in the extensive system of national parks and biological reserves spread across the country having stunning ecological variety. National Geographic has called it "the most biologically intense place on Earth".
This park conserves the largest forest on the American Pacific coastline and one of the few remaining sizeable areas of lowland tropical rainforests in the world. Corcovado is large enough to support a sizeable population of the endangered Baird's Tapir and holds about 140 species of mammals, several big cats including jaguars, ocelots, cougars and margay. Costa Rica as a whole is an ornithologist's dream holding several hundred bird species. At the center is a crocodile filled lagoon, making a visit here a thrilling part.
The wildlife can in part be explained by the variety of vegetation types including montane forest, cloud forest, jolillo forest, prairie forest, alluvial plains forest, swamp forest, freshwater herbaceous swamp and mangrove, together holding over 500 tree species, including purple heart, poponjoche, nargusta, banak, cow tree, espave and crabwood.

Poas Volcano National Park
Poas Volcano National Park made of volcanic rocks reaching 2.708 Mts. of height. Located at the Cordillera Volcánica Central, 37km north of Alajuela province, one of the spectacular volcanoes of the country and is an extraordinary scenic beauty most visited places by national and international tourism. Although its activity is considerably different than Arenal Volcano, Poás is another of Costa Rica's most active volcanoes having lake inside one of its explosion craters.
There is a long history of eruptions, one of that is the one in 1910, consisting in a huge ash cloud that reaches 8.000 Mts.

Palo Verde National Park
Palo Verde National Park is one of the best wildlife and a bird-watching park in Costa Rica and is an undiscovered jewel in the Costa Rican park system.The Palo Verde National Park protects forested areas as well as an extensive marshland between the Tempisque and Bebedero rivers of Guanacaste.

Barra Honda Caverns
Unlike the volcanic stone found throughout northern Costa Rica, the Barra Honda area of the Tempisque Basin has a foundation of limestone. The best known feature is the water cut caves through the small mountains of the park.
The protected tropical dry forest within its borders is some of the last in the world, and very different from the rain and cloud forests that attract many ecological tourists to Costa Rica.
The soda straws, roses, pearls, needles, cave grapes, terraces, curtains, stalactites, stalagmites and other calcareous formations of the more than 40 limestone caverns are the main attraction at Barra Honda National Park.

Santa Rosa National Park
Santa Rosa National Park is one of the most important historic areas, in addition to serving as a popular destination for nature lovers and surfers, in Costa Rica. The beautiful Nancite and Naranjo beaches are major nesting grounds for the olive ridley, leatherback and pacific green sea turtles. The Naranjo beach is open to the public unlike the Nancite beach which requires special permits, particularly during the time the olive-ridley turtles are nesting.