Thousands of ice age bones were found at Indiana Caverns in Corydon, Indiana.
That's close to the Kentucky border near Louisville.
Cavern officials say the bones belong to a bear, pigeons, porcupines, snakes and other animals.
The rare discovery is attracting the attention of scientists from across the country.
"In fact one of the paleontologists said this may end up being the most significant bone-finding in Indiana state history and possibly in the Midwest," said Rob Houchens, Indiana Caverns.
More excavations are planned at the site.
Indiana caverns stretch for more than 38 miles underground.
Less than one mile of that is open to the public for tours.