Wyoming's Natural Trap Cave may not look like much from the surface. In fact, its 15-foot wide entrance is virtually impossible to see until it's directly underfoot. Yet held within this 85-foot deep cave is a macabre treasure: tens of thousands of animal bones, some of them more than 100,000 years old.

This death pit of a cave has been closed to the public, and to scientists, for the past four decades. But starting Monday researchers will be free to study the bones and the wealth of information they contain, the Associated Press reports.

Scientists believe that for thousands and thousands of years the cave was located along a major wildlife corridor. Over time, animals would plummet through its narrow opening. This is how a layer of bones 30-feet deep came to line its bottom. Bones found during previous expeditions—before the cave was sealed shut in the 70s—include those from mammoth, short-faced bear, collared lemming, lion, cheetah and camel, according to the National Park Service.

But the last excavations were carried out before the advent of modern genetic techniques. New research efforts will examine DNA from the animals, which could help explain how the animals are related—both to each other and to modern animals. The researchers, led by Des Moines University paleontologist Julie Meachen, said that this genetic data along with other information, such as clues about the region's historical climate, will help them better understand why so many of these strange animals went extinct during the late Pleistocene, some 11,000 years ago.

The cave is particularly well-suited for this kind of study. There is a bevy of bones, and cool temperatures in the cave have kept them well preserved. Then there's the fact that the cave is not easily accessed—you can only get to it by rappelling in on a rope—which means the remains are largely undisturbed. "It's so cold all year long, that it has got just the perfect conditions for preserving DNA, in multiple species, in large numbers of individuals," Meachen told the AP. "Which is not really found anywhere except Siberia and the Arctic."