Uley Long Barrow, locally known as Hetty Pegler's Tump, is a Neolithic burial mound that’s at least 5,000 years old. The 121-foot-long (37-meter-long) chamber was excavated and partially reconstructed in the 19th century, but it still holds its ancient secrets.

Not much is known about the old gallery grave within the Cotswolds, England. During various excavations, between 15 and 20 skeletons were recovered from its depths, though the deads’ identities is a mystery.

Apparently, those who were buried within the tomb were not always allowed to rest in peace. Roman relics, like coins and bits of broken pottery, have been found among the skeletons. It’s also believed that the grave was disturbed in medieval times as well.

Excavations and further vandalism in the 19th-century also caused a bit of damage. In 1821, workmen pilfering some stones wrecked one of its northern chambers. The tomb was somewhat restored in the 1850s by a man named John Thurman.

Today, you can still crawl inside the narrow space. You’ll want to bring a flashlight, as it can get pretty dark and eerie inside the enigmatic prehistoric burial place.