An ancient Maya network of sacrificial temples in underground caves was recently discovered in Mexico’s Yucatan State.

The construction was presumably a portal for dead souls to pass into the underworld. According to National Geographic News, one cave featured a “300-foot (90-meter) concrete road that ends at a column standing in front of a body of water.”

The Maya believed that “the souls of the dead had to follow a dog with night vision on a horrific and watery path and endure myriad challenges before they could rest in the afterlife,” leading experts to speculate whether the underground world inspired the Maya mythology, or it was - in fact - Maya mythology that created these underground spaces.