Picture a band of explorers deep underground in huge dwarven underground complex they have been exploring for what to most of them feels like an eternity. They come to hub like chamber with a dozen or so openings to tunnels apparently identical to the one they came from. The elf groans: "We will never find the surface again and feel the sun and wind on our skin."
The dwarf gives the elf a contemptuous glance, grunts, and points to an opening indistinguishable from its peers: "Nearest exit to surface, that way, one hour of walking. No water en route." He then points another opening and continues: "Alternate exit, one and a half hours. Fresh water only half hour away."
Elf eyes the indicated openings with suspicion. Snorts and asks: "And did the stones themselves speak to you and tell you this?" The answer is short and curt: "Yes."
So, underground complexes can grow to be confusing if they become large. People living in such would need a system for, well, not getting lost every time they go away from their daily route. With the underground usually described as fairly hostile, they would want to make this assist unavailable to invaders and then fill their structure with weird dead ends and traps.
While inhabitants of a particular area might rely on memorization — dwarves would probably be awesome in remembering tunnel topology — any confusion might get even the locals lost at a bad time when the structure was deliberately designed to confuse. So subtle form of memory assist that prevents anyone who can use it from losing sense of direction and going around circles would have value.
Is it possible to encode such data into the architecture itself in an non-obvious way? What architectural features would be usable for such subtle encoding? How much information could be encoded? What information would be most useful to encode? Can a trivial cipher be included, so that even outsiders who know about the code will need to wander around for some time before they can fully read the local code?