And to what part of the Dungeon Masters Guide am I referring? Why the following illustrations from the random dungeon generation section, of course (how appropriate!)
These two illustrations are not necessarily contiguous, but as they run across the bottom of two successive pages, I naturally thought of cramming them together. The first pic is represented by the northwest portion of the geomorph (the illustration vaguely hints at the chasm and the adjoining path). I added some caves for the kobolds or other denizens.
The second drawing is represented by the southeast portion of the geomorph, with a squarish structure and a stair that leads up to a raised section of the cavern. The final element that connects to the troll house in the northeast comes from a third illustration in the Dungeon Masters Guide - a classic water trap (with sliding doors)!