Northwest of present-day Puerto Natales, on the shores of the Fiordo Eberhard inlet, the Pleistocene ground sloth known as the mylodon (Mylodon darwini) took shelter in this wave-cut grotto some 30 meters high and 80 meters wide at its mouth, and 200 meters deep. The mylodon has been extinct for nearly as long as humans have inhabited the area—some 11,000 years—but the discovery of its remains caused a sensation in Europe, as their state of preservation led some scientists to speculate the animal might still be alive.

The mylodon has gained a spot in the Western imagination, among scientists and the lay public. U.S. archaeologist Junius Bird described the animal in his journals, published as Travel and Archaeology in South Chile (University of Iowa Press, 1988), edited by John Hyslop of the American Museum of Natural History. Family tales inspired Bruce Chatwin to write his masterpiece In Patagonia, which relates far-fetched legends that Paleo-Indians penned the mylodon in the cave and that some animals survived into the 19th century.

Open 8 a.m.–8 p.m. daily, Conaf’s Museo de Sitio has excellent information on the 192-hectare park, which attracted nearly 46,000 visitors in 2003, more than half of them Chilean. A tacky life-size mylodon statue stands in the cave itself.

Summer admission costs US$5.50 for adult foreigners, US$2.75 for Chilean residents, with nominal rates for children. Natales-based tours take in the sight, but there is no scheduled public transport; mountain-bike rental could be a good option. In addition to the park’s picnic area, there’s now a good restaurant nearby.