Contest #928 Hint

Ok, 2 weeks in a row with a late hint. You guys are going to have to fire me someday…

This place, among many other things, serves as a shrine of a man who was martyred here in the 5th century AD. This man was a former bad guy, a thief and possibly a murderer, who converted here and eventually died here, giving his life because his past made him the most obvious choice to die a violent death. His relics are stored kept here.