I once did an elemental-themed dungeon consisting of just six cube-shaped rooms once. Each room had an elemental flavor (fire, earth, water, air, darkness/negative energy, light/positive energy). Each room also had four doors, one in the center of each wall (that is, high up in most rooms)
Each room had certain environmental dangers (don't touch any of the suspended orbs in the zero-g environment of the air room, or you'll get shocked; the fire room is really hot; etc.), and they all contained an appropriately themed monster.
Keys and locks were to be found in each room, making sure each was visited at least twice, since all the locks had to be opened at some point. Opening a lock also deactivated some of the dangerous features in another room, making navigation there much easier. The order in which the rooms were visited thus had a certain impact, but wasn't critical.
The rooms were connected as if they were the faces of a d6, although gravity pointed to the ground in each room (except the air one), and there wasn't any noticable vertigo when switching rooms - magic makes it possible, I figured. I just rolled one to see where the party first entered. The party was hella freaked out when they got back to the first room after going left-left-left, and actually took a looong while to figure it out.
Was a nice little adventure, took us through a fun and entertaining evening. Especially since the seventh room (in the cube's center) contained a puzzle within a puzzle: Open an adamantine door in an antimagic zone, guarded by a powerful golem. The solution was to avoid the golem's patterned attacks (possible after a few tries), jump or climb on its back while it's occupied with another target, and pry loose its powering crystal, deactivating it. That crystal then had to be realigned in the golem's control panel (a simple graphic puzzle I came up with), putting the golem under a PC's control. The golem was strong enough to open the door. Voilà! Solved the dungeon, found the portal, and got outta there.
