In 2018, archaeologists discovered a network of underground lakes beneath the foundations of the Basilica of Saint John and Paul on Celius Hill in Rome. The church was built in 1100 on the ruins of the enormous Roman Temple of Claudius from the 1st century CE.
The water in the lakes is crystal clear. Scientists believe that the underground network of caves may be even more than 2 km long, and the corridors are 8 to 1.5 meters wide. Investigators will continue to explore the mysterious place. It is believed that the materials from these tunnels were used to build the great Temple of Claudius.
Such a quarry is a rarity in the center of ancient Rome. According to specialists, usually the Romans conducted mining outside the city.