Trondheim
tr...
Should be read from right to left, mirrored. It's hard to interpret just by two runes, but one of the explanations is that it's short for "trotin" = "dróttinn" = The Lord. Or it could be just scribble....
It's not just runic inscriptions on the walls of the cathedral - it's all kinds of scribble from medieval times until modern times. Below this inscription is the tr... of N 476.
