Mammoth Site of Hot Springs

In 1974, a construction worker's blade struck something white in a South Dakota hillside — a tusk, sliced clean. What followed was the discovery of a prehistoric sinkhole, now enclosed and actively excavated, holding the remains of 61 mammoths and at least 87 other Late Ice Age animals. The site is the world's largest mammoth research facility. It runs without ongoing federal, state, or local funding. Go because the dig is still happening — this isn't a diorama.