If your time in Costa Rica permits additional travel this is a list of some of the must visit destinations.
Arenal is the most active volcano in Costa Rica and in the western hemisphere. The town at the base of the volcano is La Fortuna. There are numerous lodges from quaint to deluxe where you can view the volcano activity. Definitely visit one of the hot springs in the area, either Tabacon which is more upscale with a spa or Ecotermales which is more low-key and by reservation only.
With an elevation 12,539 feet, Chirripo Grande is the highest peak in Costa Rica. The Cordillera Talamanca (this area) is unusual for Central America because it consists of folded rather than volcanic mountains. The mountains are made of metamorphic and granite rocks. To hike to the peak, you begin near the large town of San Isidro de el General, located west of the peak and national park. This is at least an overnight trip and you will need to reserve often months in advance with the national park service. It is a spectacular and challenging hike with the first day taking anywhere from seven to 12 hours to reach the base camp refuge. With good weather you will be rewarded with breath-taking views.
This is located on the most southwestern point in Costa Rica so not a day trip. Located on the Osa Peninsula, the Corcovado National Park has been called one of the most bio-diverse places on earth. Combined with Drake Bay where you can whale watch, this area has become an ecotourism hot spot.
In the highlands near San José, the quaint towns of Grecia, Sarchi and San Ramon provide a wonderful day trip. These are genuine agricultural communities where you can get a up close view of the Tico culture. Sarchi is well known for its beautiful hand crafted wooden objects.
This IS a cloud forest so it is often shrouded in clouds. The Monteverde Cloud Forest Reserve provides a unique sense of adventure and mystery partly because it is not easy to get to and partly because a cloud forest has animals and plant life that is not seen anywhere else. Monteverde is home to more than 3,000 species of animals and plants.
The laid-back and colorful town of Puerto Viejo is on the Caribbean side of Costa Rica. It has a Jamaican influence from earlier settlers. There are beautiful beaches, swimming, surfing (seasonal), mountain biking, horseback riding and tours to indigenous communities. Cahuita National Park is near and protects Costa Rica's largest coral reef.
The Rincon de la Vieja is an active volcano in the northwest of Costa Rica and is also a national park. This area of Costa Rica offers dramatic scenery, waterfalls, hot springs, bubbling mud pits (good for the skin) and wonderful hiking.
The Tortuguero National Park is an important turtle breeding ground in the Caribbean. This is the habitat and nesting ground of four of the eight species of marine turtles in the world. You can experience excursions into meandering rivers and lagoons. The area is also home to the shy West Indian manatee.