Mylodon Cave Natural Monument is a park about 25 km from Puerto Natales. The name comes from the animal that once lived in the cave, the Milodon, a large sloth like animal which went extinct about 10,000 years ago. The cave was also used by the first inhabitants of the area who arrived about 11,000 years ago. We (humans) arrive 11k years ago, sloth goes extinct 1k years later. Seems to be a trend, although the ice age didn't help. The cave was formed by wave and water erosion from a large glacial lake. The rock is an unusual conglomerate material that looks almost exactly like concrete with fist sized rocks for aggregate. The 3rd picture with the arriving tour group helps give a scale to the cave.