The Messel pit is a disused quarry near the village of Messel about 35 km (22 mi) southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of well-preserved fossils of the Messel Formation dating from the middle of the Eocene, it has significant geological and scientific importance. Over 1000 species of plants and animals have been found at the site. After almost becoming a landfill, strong local resistance eventually stopped these plans and the Messel pit was declared a UNESCO World Heritage Site on 9 December 1995. Significant scientific discoveries about the early evolution of mammals and birds are still being made at the Messel pit, and the site has increasingly become a tourist site as well.