NUST MISIS scientists and institutional collaborators have published the first results of a scan obtained by muon radiography of the underground space in the Derbent fortress of Naryn-Kala. The hypothesis of archaeologists regarding the use of the building as a Christian temple is most likely to be true. If this theory is confirmed, this building is one of the oldest churches in the world.
source https://www.lifetechnology.com/blogs/life-technology-news-blog/the-first-3-d-images-of-the-oldest-christian-church-in-russia-obtained-via-muon-radiography