When considering the number of South America's caves and caverns, Brazil takes the lion's share, not only in terms of quantity but the sheer beauty many of them bring to the surface for those willing to explore beyond eye level. No need to be an speleologist though, just being reasonably fit would do the job pretty well.
In terms of Geology, most of Brazil caves are of Limestone, with some of Quartzite as well, such as Abismo Guy Collet for instance, deepest abyss in South America - and the world - with 671 meters depth. Relatively new - explored in 2006 - it's located in Barcelos, State of Amazonas. Toca da Boa Vista (Campo Formoso, Bahia) is the longest known cave in the Southern Hemisphere. Nearby, Toca da Barriguda is Brazil's second longest.
Ubajara Grotto or Gruta de Ubajara (State of Ceara) is considered to be one of the most beautiful in Brazil, with over one km in length and having nine halls with 420 metres of lit trails. In the State of Bahia, inside the area of the Chapada Diamantina National Park, Gruta da Torrinha is well known for having the second largest flower of aragonite in the world.
Land of gold and diamonds, as its very name implies, Chapada Diamantina has everything you need if in search of prodigious caves and countless waterfalls. In terms of caverns, Poço Azul (Blue Well) takes the lead. You can snorkel and float in this 16-meters cave, its transparent crystalline blue water and submerged trees offer a breathtaking experience where you can't tell where the water ends and the rocks begin.
Poço Encantado (Enchanted Well) is another marvelous cavern to explore, at Chapada dos Veadeiros, in the vicinity of Itaetê. It's a flooded cave at the bottom of a sinkhole where sunlight falls into from April to September, however, floating is not allowed as it is in Pratinha or in Poço Azul.
Talking about records and uniqueness, Gruta Casa de Pedra (State of Sao Paulo) is nearly three kilometers long and features waht is considered to be the largest cave mouth in the world, measuring 172 meters high. Aroe-Jari (Ghost Shelter) cave is the largest sandstone cavern in Brazil, 1,550 meters long, located at Chapada dos Guimarães National Park, in the State of Mato Grosso do Sul.
By the way, while you are at it, don't leave out Gruta da Lagoa Azul (Blue Lake Cave) near Bonito, discovered by a Terena aborigine in 1924. It acquires an intense blue color during the period of the day that it is exposed to rays of sunlight. You can't float or snorkel though.
Venezuela's most famous and magnificent cave is the Guácharo (Oilbird) cave. First natural monument in the country - declared in 1949 - this 6.38 miles length is considered to be one of the most complete cave ecosystems on earth, with incredible stalactites and stalagmites formations.
Colombia's own version is Cueva de los Guácharos National Park, oldest national park in the country, located in the departments of Huila and Caquetá, close to the city of Florencia. Other highlights in the country in this regard is the Cueva de Vaca (Cows cave) close to San Gil, Santander.
However, it's not apt to the faint of heart, you will need to get down and dirty, even dive some. For a less challenging caving experience, try the nearby Cueva Indio instead.
Ecuador boasts Cueva de los Tayos (Cave of the Oilbirds) in the Morona-Santiago province. It has three entrances, the largest is a 65 meter deep shaft leading to 4.6 kilometers of spacious passages and a chamber measuring 90 meters by 240 meters. The Jumandi caves are another highlight if you want to explore South America caves and caverns, located just outside the city of Tena, in the town of Archidona.
Gruta de Huagapo, also knonw as La Gruta que Llora, Sima de Racas Marca or Sima de Milpo is one of Peru's longest caves, not far from the city of Tarma. The first 400 meters are open to the general public, beyond that you'll need a guide and special equipment, including scuba diving gear. The top cave is regarded as very difficult due to the flooded sections.
But is the limestone cave of Sima Pumaqucha (Cima Pumacocha) - from the Quechua "puma" cougar, puma, "qucha" lake - the one considered one of the deepest in South America, in the Yauyos province of central Peru, near the village of Laraos. In the year 2002, a team of cavers reached the sump at 638 meters.
One of the longest and deepest caves in Bolivia is Umajalanta - 4,600 m long and 164 m deep - at Torotoro National Park. The park is also famous for having more than 2,500 dinosaur footprints from the Cretaceous period, 120 million years ago. Chiflonqaqa (Chiflon Qaqa) cave is another attraction, with perfectly conserved stalactites and stalagmites.
Chile's Marble Cathedral is something you wouldn't want to miss, set in the General Carrera lake, second largest freshwater lake in South America. This incredible cave network have been formed by flowing water over thousands of years. Not easy to reach though, you'll need to fly to Santiago and then down to the nearest city - Coyhaique - to drive dirt roads for about 200 miles.
Further down south, at Puerto Natales - 270 km (168 mi) north of Punta Arenas - Cueva del Milodón Natural Monument was discovered in 1895 by Hermann Eberhard. The name - Mylodon (Mylodon darwini) - comes from an extinct animal which died over 13,000 years ago, at the end of the Pleistocene Era.
Argentina's Cueva de las Manos - Cave of Hands - contains an exceptional assemblage of cave art. It gets its name from the cluster of stenciled outlines of human hands that appear on the cave walls, made by hunter-gatherer communities estimated to have lived between 13,000 and 9,500 years ago.
It's located in Río Pinturas, in the province of Santa Cruz, Argentina, 163 km south of the town of Perito Moreno.
The Palace Cave - Gruta del Palacio - is Uruguay's Jewel of the Crown when it comes to South America caves and caverns. It is conformed by a series of connected sandstone caves dating back to the Upper Cretaceous epoch, about 90 million years ago.
Cueva del Palacio is located in the Flores Department, whose capital is Trinidad, a region that has has many sites of prehistoric rock art, particularly concentrated at Chamangá.