Originally a supply depot for Union forces in Kentucky, Camp Nelson became the site where 10,000 Black soldiers trained in the Civil War. But in the war’s last months, these soldiers were attacked by bitter Southerners. Their remains have never been found, and a team is dedicated to finding them to memorialize their service and heroism.

A mining operation in Cerrejon, Northern Colombia, opened a window onto a previously unknown period of the earth’s history and a world teeming with giant creatures emerged. The biggest of all was Titanoboa a 43-foot snake, the largest that ever lived. But new discoveries in Cerrejon suggest that Titanoboa’s rule was challenged by a giant crocodilian.

Leonardo da Vinci is well known for his inventions as well as his art. But new evidence shows that many of his ideas were realized long before he sketched them out in his notebooks — some even 1,700 years before. Was Leonardo a copycat?