Vaults

[hxy]

Visiting the Vaults for the first time
Should I expect every square or rectangular structure to have a door?
I see that a lot of them have, but magic mapping shows nothing...

[Zicher]

Enjoy your stay .
And no, not every square has a door, and in fact, I can't recall ever to find any secret doors in the regular Vaults structure.

[KoboldLord]

A few of the solid-looking rectangles will have secret doors. Most will not. A few of the ones that do not will still have empty space inside that you can teleport into, but again, most will not. There's unlikely to be much in the way of treasure inside them, however, and the ones with only empty space inside are just as likely to contain closely-packed out-of-depth monsters as they are treasure.

[hxy]

... contain closely-packed out-of-depth monsters...

the "out-of-depth" part worries me a bit... maybe I'll come back with a wand of digging after I gain a few more levels