Ten meters below the streets of Naples lie the ruins of ancient Neapolis, built by the Greeks around the late 10st millennium BC.However, in densely populated areas of large cities such as Naples, consideration must be given to the safety of buildings and roads, making archaeological surveys by excavation extremely difficult.

　In such an urban environment, "cosmic ray imaging" technology, which visualizes the interior of objects by utilizing the high penetrating power of muons, elementary particles generated in the upper atmosphere, is suitable.Cosmic ray imaging is an excellent technology for nondestructive visualization of underground structures, and our group has so far reported the discovery of an unknown space inside the Pyramid of Khufu in Egypt using this technology.

　This group hypothesized that an unknown burial chamber exists in the underground remains of Naples, and explored it using cosmic ray imaging.As a result, we detected a muon excess region that could not be explained by the known underground structure, and estimated the size of the cavity indicated by the excess region and its position in the underground space. It turned out to be a new burial chamber measuring meters.

　This study visualizes underground remains with a complex three-dimensional structure using cosmic ray imaging, and newly discovers a burial chamber from the Greek era. .

　In addition, it can be said that cosmic ray imaging is an extremely effective means of understanding subsurface structures.Since underground caverns are the cause of approximately 9,000 cave-in accidents in Japan each year, cosmic ray imaging is expected to be applied to new disaster prevention technologies, such as exploration of underground caverns that cause such accidents.

Paper information:[Scientific Reports] Hidden chamber discovery in the underground Hellenistic necropolis of Neapolis by muography