Archaeologists Use Radar Mapping and Sound Tests to Locate an Ancient Inca Underground Tunnel in Peru

Archaeologists had confirmed there was an underground tunnel network beneath Cusco, Peru, from the ancient Inca Temple of the Sun to the fortress of Sacsayhuamán, stated the Association of Archaeologists of Peru. These were the validation of rumors and historical texts recorded centuries ago regarding these subterranean passages. The labyrinth, in the Quechua language, called "chincana," stretches for some 1,750 meters under the city. The main tunnel, about 8.5 feet wide and 5.2 feet high, is sufficient evidence of the engineering capability of the Inca, stated Popular Mechanics.
🚨Tunnels Found Under Sacsayhuaman🚨
— Ancient Hypotheses (@AncientEpoch) January 15, 2025
An archeological team in Cusco has announced a discovery of trapezoidal tunnels under the famed site at Sacsayhuaman. The project titled "Proyecto de Investigación Arqueológica Chincana" Made this announcement in a press conference a few days… pic.twitter.com/B6DlwwAo2n
The breakthrough came after the painstaking research led by archaeologists, Jorge Calero Flores and Mildred Fernández Palomino, of ancient documents, especially a chronicle from 1600 that told about the deep "cave" across the entire city of Cusco made by Inca kings. These underground structures had been deliberately left intact during the building of a church above the so-called Temple of the Sun by the Spanish colonizers. The methodology for the research combined historical research and modern technology. The team consulted more than 1,600 texts and took the advice of historian, Manuel Chavez Ballon, considered the father of Cusco archaeology. The suggestion by Ballon to look even underneath the sidewalks was just what led to the discovery, stated Colombia One.

The archaeologists, using innovative detection methods, conducted sound tests by striking metal plates against the ground every 50 centimeters along suspected routes. The echoes indicated caverns beneath and thus the ground-penetrating radar mapping. The radar images revealed the tunnel running from 1.4 to 2.5 meters deep. Besides the Temple of the Sun and Sacsayhuamán, this underground network connects several major ancient points of interest, such as Muyumarca and Calispuquio. Researchers think that the subterranean system reproduces what is aboveground, the layout of the streets of old Cusco, and testifies to the complexity of Inca urbanism.

This technique, using the cut-and-cover method, has the Inca builders digging trenches, lining them with stone walls, and topping them with carved-beam ceilings. The size of the tunnel would indicate that perhaps even the nobles in the litter could negotiate this passage and that it would serve as protection for them while going from one culturally important site to another.
Graham, the archaeologists followed 16th-18th c Spanish and Jezuit documents describing in details what used to be Chincana, a palace with Sun baths and the tunnel discovered a probable drainage channel
— K@t@- Indonesian Heritage & Prehistory (@kallinikos1980) January 18, 2025
This discovery adds another layer to understanding the city's significance as a capital of the Inca Empire, with a population peak of about 12 million between the 15th and 16th centuries. With only 130 miles separating it from the famous Machu Picchu, Cusco is still disclosing its archaeological treasure, according to Smithsonian Magazine. The research team plans to begin excavations at key points of the 'chincana' in March, hoping to physically enter and further document this remarkable feat of ancient engineering. Their work promises to shed new light on the sophisticated urban planning and architectural achievements of the Inca civilization.