Archaeologists revealed on Wednesday they have discovered a pyramid, which is inside a pyramid, which is inside another pyramid in Mexico.

The multi-layered monument, also known as El Castillo, or the Temple of Kukulcan, can be found at Chichén Itzá, the complex of Mayan ruins in Mexico's Yucatán Peninsula. Archaeologists from the US discovered the second pyramid back in the 1930s, not knowing this was just the beginning of the story.

Now, using 3D electrical tomography imaging technology, experts have discovered yet another layer to the pyramid-ception.

"It's built like a Russian nesting doll. Under the large one we get another and another," chief researcher Rene Chavez Seguro told a news conference in Yucatán, AFP reports.

The newly discovered smallest pyramid was built between 550 CE and 800 CE, at the apex of the Classic Period of Mayan civilization. The middle pyramid was built somewhere between 800 CE to 1000 CE and the largest outer pyramid dates from around 1050 CE to 1300 CE. This means the small inside pyramid could act as a neatly preserved insight into the life of the Maya from this particular period.

The small pyramid measures around 10 meters (33 feet) tall, nestled inside a 20 meter (65.6 foot) structure, topped with a 30 meter (98.5 foot) exterior.

The researchers have a few theories as to why the monument was built in such an eccentric way. For one, it could simply be a kind of renovation of the old monument. Alternatively, it could have been used to mark the arrival of a new leader, as if to erase the past from the city’s memory.

Representatives from Mexico's National Institute of Anthropology and History explain that the Maya didn't destroy the originals buildings because they believed they had a connection to the spiritual world. Understandably, the ancient people were keen not to get on the wrong inside of this realm.