Peruvian archaeologists have discovered a sealed underground corridor known as “the condor’s passageway”, dating back to the Chavin civilisation.
They are known for having built granite and limestone temples with complex drainage systems to prevent flooding, as well as creating sculptures from carefully hammered sheets of gold.
Their metalsmiths developed an understanding of melting points, soldering and creating alloys, which was impressive for the time.
The corridor, one of dozens at the site that are linked to underground structures, is about 3,000 years old. Explorers used a camera mounted on a robot to investigate the tunnel, which is thought to be at risk of collapse.
Legend of the Lanzon
About 430km north of Lima, the Chavin de Huantar archaeological site is among the culture's most important, and thrived from about 1,500 to 550 BC.
The area, which became a Unesco World Heritage Site in 1985, contains about 35 tunnels that have been discovered over decades of excavations.
The Chavin de Huantar is filled with carvings of animals thought to have religious significance, including jaguars and caymans. At the centre of the complex of buildings is the Lanzon, a holy stone sculpture sited in a network of tunnels, which features a carving of a hybrid human-jaguar figure.
It is thought worshippers would walk through the dark tunnels before eventually being confronted with the Lanzon and performing religious rituals.
“What we have here has been frozen in time,” lead archaeologist John Rick told Reuters.
Mr Rick has been studying the area for nearly 30 years and says the world of carvings, sculptures, tunnels and roaring sounds from water flowing through specially created canals represents is an example of an early effort by authoritarian rulers to control their subjects.
“I was fascinated with the evidence we have for this idea of manipulation of people who went through ritual experiences in these structures,” he told Stanford News in 2016.
The religious order in the Chavin civilisation “needed to create a new world, one in which the settings, objects, actions and senses all argue for the presence of intrinsic authority”, he said at the time.
A large ceramic piece weighing about 17kg, decorated with what appears to be a condor's head and wings, was found in the aisle, along with a ceramic bowl, both unearthed in May last year when the entrance was uncovered.
The condor, one of the largest birds in the world, was associated with power and prosperity in ancient Andean cultures.
Mr Rick, a Stanford University archaeologist, has said much of the temple complex is still to be excavated.
Agencies contributed to this report