Last September photographer Elio Della Ferrera spotted thousands of dinosaur tracks traversing vertical rock faces in the Fraele Valley of Stelvio National Park, high in the Italian Alps. Some of the prints, spanning as many as 40 centimeters across, date back about 210 million years, making the newly identified site one of the richest deposits of Triassic dinosaur tracks in the world.

The footprints are so well preserved that “it took me a few seconds to realize the photos were real,” says paleontologist Cristiano Dal Sasso of the Natural History Museum of Milan, who is leading the investigation of the site. “Now we can go back in time and study the evolution of dinosaurs in this place.”

In a preliminary study, Dal Sasso and his team deduced that the prints were made by herds of large, herbivorous dinosaurs, probably prosauropods, ancestors of Jurassic sauropods such as Brontosaurus. The tracks formed when dinosaurs walked across muddy tidal flats along the shores of the prehistoric Tethys Ocean, long before the Alps rose.

Studying this newly named “Triassic Park” will be challenging because it is so difficult to access, Dal Sasso says—researchers will have to rely on drones and remote sensing to study and digitally preserve the footprints.