A visit to Parque Nacional Volac�n Arenal makes a great day trip from San Jos�. As this area of Costa Rica is known for its outstanding volcanoes, a visit to the area wouldn't be complete without seeing one. An active volcano, the Arenal is the youngest in the nation and actually one of the ten most active in the world since massively erupting in 1968. Depending on the weather, you may or may not be able to catch a glimpse of the eruptions as Arenal is usually surrounded by clouds which often produce rain. However, nighttime viewing can prove quite impressive.