Caves are not particularly common in South America and these notes are intended to help anyone suffering withdrawal symptoms whilst wandering down there, doing their bit to widen the Gringo Trail.
(Also known as Eberhardt's Cave and the Cave at Last Hope Sound.)
This is a must for anyone visiting the Paine Towers National Park in Southern Patagonia and is a healthy contender for the most southerly cave in the world, being at 52° South. It is reached by following the road north from Puerto Natales for 20km until a track off to the left is signposted to the cave, this leads directly to the entrance after 8km. There is just sufficient traffic to hitch there and back in a day - the only alternative being a taxi. For further details on the region consult the South American Handbook .
The cave is famous for its remains of a Mylodon (an extinct giant ground sloth) which were dessicated by the dry, cold weather. They were brought back to England in 1895 and can still be seen in the British Museum (Natural History). Particularly impressive is the dried dung - radio carbon dated to 10830 ± 400 B.C. In rememberance of this find, the Chileans have erected a 3m high model of a Mylodon in the entrance to the cave. Bruce Chatwin's book  is very useful in discussing the history of the cave - indeed his travels in these parts were inspired by it.
The cave is at the foot of a large crag and gives the impression of an old phreatic resurgence, but it is clearly not. It seems likely that it was formed at the edge of a glacier which carved out Seno Ultimo Esperanza. The entrance is 20m high and 30m wide and the cave extends back for 200m, never really getting out of daylight. I carefully checked for extensions, but there are none. the rock is a calcite-cemented conglomerate of fist-sized, well rounded pebbles - a formation which I think covers a wide area in these parts. The cave was formed by solution of the calcite cement and the floor is covered with many of the pebbles. There are some stalactites near the entrance (although these may be birds' nests), but the whole cave is now completely dry. there is also a smaller cave nearby, but it seems that these were formed as one-offs and not as part of a Karst drainage area. Further prospects for exploration appear limited.
The area concerned lies 1° South of the equator on the eastern side of the Andes at the edge of the Amazon basin. Gringos in the region are most likely to be visiting Misahuillio' (120km S.E. of Quito) which is the cheapest place in South America to go on a "jungle trip". Whilst in the area there are some interesting caves to be seen. The most famous is the Jumandi Cave which has been visited by, amongst others, a Southampton University party in 1979 . This lies 4km north of Archidona, 100km off the Tena-Baeza road and is easily reached by the local bus (but isn't signposted). The resurgence waters have been dammed outside the entrance to provide a useful swimming pool. There is a water pipe to supply the locals which can be followed into the cave, but I declined to go any further than 100m in, because it would have meant wet feet. The cave is 1.3km long and significant in the drainage of the area, but whether any other finds have been made in the area, I am not sure. Talking to the locals revealed that there are many caves in the area around Puerto Napo (5km south of Tena and on the Rio Napo). One of these was found accidentally whilst locking for a waterfall - it is mentioned not for its inherent interest, but because I believe it to be typical of many in the area. The Cueva del Rio Lata lies 4km above river level on the true right bank of the Rio Lata (apparently a common river name); 25m upstream from the bridge on the Puerto Napo-Misahuillio' road (about halfway between the two towns and near the "Granja Experimental"). The dry entrance lies just above a small rocky resurgence (possibly the water seen later in the cave) and heads directly into the hillside for 70m until it splits: the left hand branch leading after 20m to a pool and a small active inlet above, which gets too small. Right leads to a low bedding plane breakdown region. the water from the left branch sinks just past the junction. Although only 100m long, the cave has some pretty stalactites near the entrance and a colony of half a dozen very noisy (and frightening) bats.
The waterfall lies 1km further up river and is well worth seeing - straight from a "Bounty" advert. Oil geologists had left a series of painted survey stations up the river, and it may be that they know more about the area and have detailed maps (which are not otherwise available). Although the depth potential of the area is only 300m or so, there are undoubtedly many caves waiting to be found, and an overall survey could be tackled by one or two people with limited equipment, who are otherwise travelling. Misahuillio' is a very pleasant place to stay, with beer at 8p a pint (not quite up to english standards - it is marked "bebida de moderacioni", which I first took to be a health warning, but I think it refers to the strength). Locals tell of a Russian (could they mean Polish?) expedition which found caves 300m deep in Morona Santiago Province (which lies to the south, capital Macas). Although a full-blown expedition to the area would be very expensive, a couple of individuals could do much useful work finding entrances and assessing potential.
 The South American Handbook. Issued annually by Trade and Travel Publications, Bath.
 In Patagonia. Bruce Chatwin (Picador).
 The Jumandi Cave of Ecuador. P. Brown and P. D Brown, BCRA Caves and Caving 14 (Nov. 1981) pp 26-28