Go to the Butterfly Garden in Monteverde. Monteverde is a quaint mountain town with a large amount of Quakers (who immigrated to Costa Rica from the American South in the1950s to escape Korean War drafting). The butterfly garden is a popular destination in the town, with a vast and exquisite collection of colorful and exotic butterflies. You can witness the life cycle of butterflies here and learn many interesting facts from the experts at the garden.
Visit the Cloud Forest Biological Reserve. While in Monteverde, another popular attraction is the Cloud Forest, which has been well-preserved by the local Quakers. The cloud forest is very similar to a rainforest but is much more humid. It's a great place to go hiking and explore the simplicity and beauty of the Costa Rican nature. There are excellent sky canopy tours available in the forest as well.
Explore Irazu Volcano National Park. The Irazu Volcano is the tallest active volcano in the country. There have been eruptions at Irazu since 1723. This national park has been in existence since 1955, and has an ethereal, almost space-like atmosphere, with it craters and sparse landscape. There are trails leading to the craters at the summit, and lots of volcanic rock scattered everywhere. This is one of the most popular attractions in Costa Rica, and is a very otherworldly experience.
Spend the day at Manuel Antonio National Park. Located on Costa Rica's Pacific coast, Manuel Antonio is a popular national park that consists of various beaches and hiking trails. The natural beauty of the park is astounding, as well as the immense array of wildlife. Visitors can get up close looks at animals from capuchins to ghost crabs.
Go swimming at Playa del Coco in Guanacaste. This beach is a very relaxed and laid back area, and is a great place to sunbathe, go swimming, snorkeling, fishing, or surfing. The beach town also has a very active nightlife scene. With the exquisite beach and the selection of restaurants and activities here, this is the ideal place to relax--Costa Rican style.