There are countless tour operators who offer excursions by bus to nearby attractions.  You can also take public transportation to many or rent a car.

Heredia, best known for Language Schools, is a quiet colonial city on the slopes of Volcán Barva.

 

Atenas, declared the Best Climate in the world by National Geographic, is an agricultural town with spring-like climate year round.

Cartago, the nation's first city, was once Capital of Costa Rica. In 1910 earthquakes destroyed much of the city, but many old buidings remain. "Las Ruinas" are the ruins of the Iglesia de la Parroquia and the spectacularly beautiful Orosi Valley is nearby

 

Poás Volcano, one of the largest active craters in the world, also has hiking trails to a cold water lake

Grecia and Sarchí are two mountain towns: Grecia is known for its red metal church, Sarchí for its hand painted ox carts.

 

Irazu Volano, north of Cartago, has dozens of dairy farms on its slopes. It last erupted in 1994. At 11,300 feet and appearing more like a mountain range than a single volcano, Irazú is the largest of many volcanoes in Costa Rica, with three craters available for viewing

Bosque de Paz Rain/Cloud Forest, high in the mountains, has hiking trails to waterfalls, botanical gardens and lookout points.

 

Arenal Volcano, in the typical conical shape, is Costa Rica's most active and most visited volcano, with frequent lava flows and eruptions. A must see in Costa Rica