Lake Titicaca was a sacred space to the ancient Andean empire of the Inca, which at its height in the early 16th century controlled territory from modern-day Colombia to Chile. The Inca built more than 80 temples and other structures for a variety of rituals on the Isla del Sol, or Island of the Sun, in the southern part of the lake in Bolivia, where their origin myth said the sun god was born and their primordial ancestors emerged from a rock. And they lowered offerings into the surrounding waters as they sent up fervent prayers.

A new discovery, published today in the journal Antiquity, offers fresh insights into the Inca belief system, which was likely tied not only to politics, pleas for fertility, and a goddess known as Mama Cocha—the sea mother—but also to blood-filled offerings that clouded the waters of one of the world’s largest lakes.

During an underwater survey of the lake, which straddles Bolivia and Peru, an international team of archaeologists recovered an offering box made of andesite, a local volcanic stone, that was lying on a reef some 18 feet below the surface of the lake. Measuring about 14 by 10 by 6.5 inches, it had a concave offering cavity that was sealed by a round stone plug, undisturbed since the box was deposited more than five centuries ago.

Inside the box, the scientists found a tiny rolled cylinder of gold sheeting and a figurine of a llama made from Spondylus, the coral-hued shell of a spiny oyster that was rare and valuable. The cylinder, the archaeologists believe, may be a miniature replica of a chipana, a type of bracelet that Inca noblemen wore on their right forearm. The llama represents the Inca’s sturdy beast of burden.

Costly offerings, multiple meanings

This wasn’t the first such discovery made in the lake. Tantalizing rumors of submerged treasure drew Spanish conquistadors to Titicaca, and one report from 1541 mentions 10 men who drowned in search of it. In modern times, divers including famed underwater explorer Jacques Cousteau have probed the waters since the 1950s.

Various expeditions through the decades have found more than two dozen stone boxes of differing shapes on another reef, but the contents were preserved, in whole or in part, in only four. Those offerings were figurines of humans, male and female, as well as llamas, and they were made of rare and valuable materials—silver, gold, and Spondylus shells. Miniature golden tupus—pins to secure Inca shawls—were found with one of those boxes, suggesting that the human figurines were originally covered in traditional, brightly colored clothing that decayed as water infiltrated the offering cavity.

“There were multiple, complimentary meanings” of the offerings, ranging from large political statements to simple agricultural requests, said the paper’s coauthor, Christophe Delaere, in an email. Delaere is the scientific director of the Université libre de Bruxelles' underwater archaeology projects at Lake Titicaca.

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Onboard a research vessel on Lake Titicaca, project director Christophe Delaere and other team members share their discovery with archaeologist Johan Reinhard.

For starters, in their reverence for the lake, the Inca were probably influenced by traditions of the people who lived there before them—the Tiwanaku, a pre-Hispanic civilization believed to have lived in present-day Bolivia, Peru, and Chile between about 200 B.C. and A.D. 1,000.

“I suspect that there were a limited number of places that the Inca made offerings, and these were made for reasons that existed prior to their occupation,” National Geographic explorer Johan Reinhard, an archaeologist specializing in pre-Hispanic sacred landscapes, said in an email. “The Incas made offerings at places that already figured in the beliefs of the people before they came to Lake Titicaca.”

The offerings were possibly linked to a cult of Inca ancestors, and to pilgrimage ceremonies that took place on the Island of the Sun. By centering their origin myth there, and making it a place for conducting rituals, the Inca were making a statement about their empire. (Archaeologists find a remarkably preserved Incan mummy: a girl, sacrificed in the Andes Mountains.)

“The ceremonial offerings made to the lake were both symbolic and political acts intended to legitimize by way of ritual the power of the Inca occupation on this sacred space,” Delaere and his co-author, Penn State archaeologist José M. Capriles, explain in their paper.

Gold and blood

On another level, the archaeologists believe the cylinder of gold may have been fastened to the llama in a nod to the Inca having expanded their empire into this gold-rich region in the mid-1400s. “The Inca believed in religious traditions that were never separate from political and economic ones,” said Reinhard, who was not part of the discovery team. “They were all inextricably linked.”

Related: Archaeologists unravel Incan records One of the great mysteries of ancient Peru is that the Inca did not have a system of writing, but communicated with a system of strings tied with knots. For the first time, centuries-old knotted textile accounting records known as quipus were found buried with well-preserved organic material. They were found at the archaeological site of Incahuasi, the base of operations for the Inca expansion along Peru’s southern coast.

It’s also possible that the newly discovered offering and others may have been associated with pleas for the fertility of llama and alpaca herds; Inca mythology said those animals originated from lakes. The Inca may also have been praying for fertility of the land and abundant harvests. Spondylus shell, which came from waters off the coast of Ecuador some 1,200 miles away, was used in rituals asking for rain because it was associated with the ocean, and with Mama Cocha, the Mother of Water goddess, both of which were believed to be linked to Lake Titicaca.

According to 17th-century Spanish cleric Alonso Ramos Gavilán, who wrote a monograph about the Inca rituals at the lake, the offerings deposited there were accompanied by waterborne clouds of blood. Sometimes a child or an animal would be sacrificed to appease the gods, and the victim’s blood was poured into the offering cavity of a box, which would then be sealed. As the box was lowered into the lake by ropes, water would seep into the cavity, mix with the blood, and billow into the lake, turning the surrounding water red. (Here's why an ancient Peruvian society sacrificed their own children.)

The recently discovered box has openings that archaeologists believe could have accommodated ropes to lower it from a boat. Did it, too, hold blood? It’s impossible to tell now, since any trace has long since washed away. But it’s entirely possible that blood was, indeed, part of the grim ritual that sent this offering to the bottom of the lake, along with the entreaties of an empire.

As scientists continue to comb the extensive depths of Lake Titicaca—which covers some 3,200 square miles—they will surely accumulate more evidence of the Incas’ strange and mysterious rituals.

“It is sometimes believed today that the entire planet has been explored, but 70 percent is covered by water,” said Delaere. “The underwater world has been very little explored and offers infinite possibilities for research and discovery.”