Caves of Garraf Nature · Olivella, Garraf, Barcelona Image of Olivella, not of the place itself. An extensive karst system in the Garraf massif, in which some 400 underground cavities have been counted between caves and potholes, making it one of the most important karst areas in Catalonia. The landscape combines surface forms, such as dolines and karren, with underground formations. Among the cavities, the Falconera stands out, a vast cave with a large underground lake, today polluted and no longer fit for swimming. Photo: Josemanuel (CC BY-SA 2.5) What to see and do in Olivella