Arecibo - Río Camuy Cave Park (Cueva Clara de Empalme)

The Río Camuy Cave Park features a very large cave system covering 268ac/109ha and thought to be the third large cave system in the world. A trolley bus transports visitors to a 200ft/61m deep cave, or sinkhole, which is now a preserved area known as Cueva Clara Empalme. The caves feature various rooms, in some cases with extremely high ceilings, stalagmites and stalactites, and rivers rushing through. A guided tour leads visitors through the Cueva Clara Empalme.

In addition to the natural wonders the cave system presents, it's also interesting to note that the caves were used by the indigenous population long ago.