The Carso Norteño (Northern Karst) is located on the northern side of the island, north of the volcanic Cordillera mountain range. The well-developed tropical cockpit karst is characteristic for the Caribbean Islands. The mogotes are isolated steep-sided residual hills composed of Montebello limestone or Oligocene Lares limestone, surrounded by nearly flat alluvial plains. In other parts of the world they are called towers or cockpits. The word mogote comes from the Basque word mokoti meaning sharp-pointed, moko means mountain peak. Several mogotes along a ridge are called pepinos.
Beneath the underground drainage, there are numerous rivers draining the area. One of them is the Rio Grande de Manati, another one Rio Camuy. Both rivers have vast systems of caves connected to them. The caves are fed by allogenic rivers which drain the volcanic Cordillera, and go underground as soon as they reach the limestone. This is a typical contact karst situation, and the results are linear cave systems with few side passages.
The Sistema del Río Encantato is the largest cave system of the island, protected by the Área Natural Protegida Río Encantado. Its resurgence is called Manatial de las Aguas Frias, the spring of the Rio Grande de Manati. It has five entrances with different names, huge gorge like river passages up to 30 m high, and three chambers which are more than 100 m in diameter. There are stalagmites, draperies and showerhead formations. The cave is known for a variety of cave live, the troglobionts include tailless scorpions of decent size called Amblypigids. Also, cockroaches, fresh water crabs and crayfish are common. The cave is visited by 10 different bat species. Despite all those spectacular fact, the cave is not listed. The reason is simple: it is actually not a tourist cave, visits always include serious caving, and as far as we know there are no cave trekking tours. But we listed a series of show caves and semi-wild caves in the area.