“Tucked away in the lush northwest corner of Puerto Rico, about 50 miles west of San Juan, is one of the island’s best kept secrets; the Rio CamuyCaves. The cave system, which gets its name from the 13-mile-long Camuy River, forms the third-largest cave system in the Western Hemisphere. The process that created the caves started almost 160 million years ago when a great limestone plateau was thrust up from the Caribbean Sea to form the western half of the island. Over time rainwater and wind eroded the surface of the plateau forming large sinkholes and rounded hummocks called magotes, characteristic of what we now call ‘karst’ landscape. The process of erosion continues today, helped along by the dense vegetation that blankets the region. Some of this vegetation produces carbon dioxide which, when absorbed by rainwater, forms a mild carbonic acid which further dissolves the porous limestone.” – Going Underground by Michael Defreitas.