Davelis Cave (Spilia Ntavelis) is a cavern on Mount Penteli long associated with the 19th-century bandit Christos Ntalias (Davelis) and later with claims of time distortion, electromagnetic anomalies, and apparitions. Visitors and researchers report missing time, malfunctioning equipment, sudden temperature shifts, and shadow figures, while the cave’s inner chambers contain Byzantine chapels and strange side tunnels that were allegedly sealed after unexplained incidents. During the Cold War, rumours of secret military experiments and tunnel collapses added a modern conspiracy layer, and Davelis Cave remains a focal point for Greek paranormal researchers, EVP sessions, and portal theories.