It's amazing how much archaeologists and explorers can still dig up about our world's ancient societies.
But sometimes, it seems like their spooky discoveries should have stayed buried.
The last terrifying artifact to be unearthed was a black sarcophagus from Alexandria, Egypt, which was revealed to contain the remains of a family buried together - for reasons that are still unknown.
Now, workers closer to home are investigating one of Mexico's most famous historical sites, after making a disturbing discovery.
The Pyramid of the Moon
Archaeologists are shedding more light on the ancient Maya civilization after uncovering a hidden section of Mexico's largest pyramid.
The Maya once ruled a large section of South and Central America, and are remembered best for their powerful kingdom between 100 BC and 750 AD.
Before they came to power, the Maya had already developed complex farming systems, a written language, and large cities with impressive temples.
In Teotihuacan, a city northeast of Mexico which was home to more than 100,000 people when the Maya reigned, they worshiped at huge structures including the Pyramids of the Sun and Moon, where archaeologists made the recent discovery.
Passage to the Underworld
Standing more than 140 feet high and measuring more than 500 feet wide at its base, the Pyramid of the Moon is still impressive thousands of years after it was built.
And there are still mysteries to be solved about this ancient landmark, now that a secret passage has been found underneath it.
Electronic scans of the pyramid, which began in 2017, revealed that a 50-foot wide chamber is hidden underneath the structure, while a passageway to the room leads under the square at the pyramid's base.
Experts from Mexico's National Institute of Anthropology and History (INAH) have not explored the hidden space yet, but say it was probably used for religious ceremonies.
In the past, the remains of sacrificed humans and hundreds of animals have been discovered in tunnels surrounding the pyramid.
Experts from INAH say the building held a symbolic connection to the Maya underworld, and that more human remains could be found in the underground chamber.
It's a grizzly suggestion, but the remains of thousands of sacrificed people have already been discovered in the nearby Plaza of Columns.
Researchers are trying to uncover a path into the hidden chamber, hoping that whatever they find inside will reveal more about this ancient civilization.
While human and animal remains are one possibility, trade goods from other parts of the Americas buried with the sacrifices could also teach us more about how the Maya lived.
[H/T: El Universal]