Map anomalies...
The lights are faint, perhaps remnants from a ancient time when this cavern was dug out.
There are some black and grey lines that are from the "tiles" joining that you can ignore.
"No Exit" is not actually written on the ground, but does mean that is a dead end.
You see
Forge, you see another sub-cavern and what may be another exit to the outside.
Nar, you see the glint of some shiny things scattered on the floor, and another one of those rubble piles.