The Arenal Observatory Lodge was built in 1987 as a research station for the Smithsonian Institute and the Universidad Nacional de Costa Rica. Located at the base of the Volcano and overlooking Lake Arenal, it is ideally situated for observing this active giant. The frequency and intensity of Arenal's eruption coupled with the "next door" proximity, make for a truly spectacular natural history experience. At night the lava flows and the ejection of glowing rock provides viewers with an impressive natural fireworks display.

From the Observatory visitors can enjoy views of nearby Arenal Lake which is the largest fresh water lake in Costa Rica and a popular place for catching guapote (rainbow bass). Boats, equipment and local guides are easily arranged for fishing of boat tours of the lake. The lake is also renowned for windsurfing due to a near constant wind at its northern end. A swim in the nearby Tabacón Hot Springs is a good way to finish the day.