(CNN) — Sprawling across the Andean mountain border between Bolivia and Peru, Lake Titicaca is a popular spot with travelers who visit the floating reed islands of the Uru people, or the religious festivals of Copacabana.

Now scientists working on South America's largest lake have revealed some of the secrets hidden below its surface, discovering a remarkable haul of artifacts from an ancient underwater ceremonial site used by the pre-Inca Tiwanaku state around 700-1000 AD.

A team of researchers led by Christophe Delaere, a marine archaeologist at the UK's University of Oxford and Belgium's Universite Libre de Bruxelles, found the remains of sacrificed juvenile llamas, ceramic incense burners shaped like pumas, and high-value offerings of gold, stone and shell ornaments.

Delaere said this is the first time that such offerings have been discovered undisturbed.

"This is one of the advantages of the immersed heritage: the lake protects its ancient material culture from time and man," he told CNN via email.

The findings provide evidence of repetitive rituals practiced by the Tiwanaku elites, according to a research report published in Proceedings of the National Academy of Sciences on April 1.

It is a discovery which reveals organized religion was present in the region earlier than previously thought, the team said.

Offerings, including the sacrifice of llamas and other animals, were expensive, and included some of the most prestigious items available in the Andes at the time.

For example, the team found the shells of spiny oysters from the coast of modern day Ecuador, which could only have been acquired through trade.

Researchers also believe that perforated gold sheets discovered at the site may have been attached to the llamas as a form of ritual regalia.

Sacrificial knives

The offerings were made as part of rituals that contributed to state building Teddy Seguin/PNAS

Delaere explained that the llama bones have marks caused by sacrificial knives, and the animals may have been sacrificed on a small island around 300 meters from the ritual site before being immersed with other artifacts.

Excavations took place in the Khoa Reef, near the Island of the Sun in Lake Titicaca.

Sometimes described as an "inland sea," the lake sits at an altitude of around 3,800 meters in the central Andes mountain range, its western half in modern day Peru and eastern in Bolivia.

It's shaped by a fault that separates the Andes into two separate mountain ranges, and the lake created a unique ecosystem that encourage human settlement, according to the research.

The area is commonly associated with the Inca civilization, but the Tiwanaku predate the Inca by around 500 years, according to a press release from Pennsylvania State University, where Jose Capriles, the study's joint author, is an assistant professor of anthropology.

Religious rituals

The spiny oyster shells come from Ecuador, some 2,000 kilometers away. Teddy Seguin/PNAS

"Our research shows that the Tiwanaku people, who developed in Lake Titicaca between 500 and 1100 AD, were the first people to offer items of value to religious deities in the area," said Capriles in the press release.

Capriles told CNN that finding the artifacts in association with each other in their primary archaeological context, rather than in a private collection, allowed researchers to make a new interpretation of how religion emerged in Tiwanaku.

"Like other formalized ancient religions, the rituals conducted by emerging elites were meant to display wealth and power but also convey moralizing values," he said via email.

"In other other words, the deities to which these offerings were made represented supernatural deities who rewarded and punished behavior that was in benefit or at the expense of the collective."

Tiwanaku state also left more than a dozen sites on the Island of the Sun, including a ceremonial complex shaped like a puma known as Chucaripupata.

The Inca were not present in the Titicaca area until around the 15th century.

From its base around Lake Titicaca, the Tiwanaku state exerted its influence over large swathes of the southern Central Andes, and these religious rituals played an important role in state building, according to researchers.