Archaeologists in Peru thought they had discovered something special when they uncovered the tomb of a pre-Inca priestess and eight other corpses in 2011. But an even bigger find was right beneath their feet.

Continuing their search for artifacts a year later, the team dug beneath the priestess, uncovering a basement tomb they believe was built by an ancient water cult and meant to flood.

"This is a very valuable finding," said Carlos Wester La Torre, head of the excavation and director of the Brüning National Archaeological Museum in the Lambayeque region—a region named after the little-known culture that built the stacked tomb. "The amount of information of this funerary complex is very important, because it changes [what we know of] the political and religious structures of the Andean region."

The nearly 800-year-old basement burial sheds light on complex Lambayeque social structures and on the worship of water in the culture.

Four sets of waterlogged human remains were found in the flooded tomb, one adorned with pearl, turquoise, and shell beads—indicators of wealth or status. The other three corpses likely were intended to accompany the body into the next world.

View Images A diagram shows a recently unearthed stacked grave of Lambayeque elites. The priestess on the first floor was found seated, while bodies on the bottom floor were found lying down, below the water table (marked by a dotted line). Image courtesy Carlos Wester La Torre, Brüning National Archaeological Museum

The faces of both elite individuals, in the lower and upper tombs, were covered with copper sheets, and wore earspools bearing similar, wavelike designs.