Direction inside the dungeon

[Juan]

Hi all, you wise delvers.

I am having trouble to determine which rolls could help a PC to know they are deviating from their needed path in a big multi level dungeon.

To give some context. There´s a mine (middle level of the mega-dungeon) which goes deep inside a mountain. If players insited to follow the corridors, how to inform them, after a succesfull roll, that the dungeon levels they know do not get that deep and maybe they are missing the point?

I guess Cartography, Observation, Prospecting skills?
or, maybe Absolute Direction, Danger sense, Intuition advantages (and no roll then)?

Thanks in advance!

PD
Making the mine smaller will not work for two reasons:
a) the deepest corridors are a good way to explain wandering monsters in all the mega-dungeon, and
b) it is quite probably they will have to delve there later