Some 26,000 years ago, the collapse of a karst sinkhole created a 60ft-deep death trap for Pleistocene mammals that dared to drink from its alluring pond. After silt filled the hole, it remained undiscovered until revealed by earth-moving equipment in 1974. Today this treasure trove of Ice Age fossils delights not only scientists but visitors, who get a primer on earth history during a 30min guided tour. Paleontologists continue to excavate this ongoing, covered dig; to date, 61 mammoths have been identified, along with numerous other creatures.