So that giant rotating bridge begs a few questions.
Firstly, what is it a bridge over? The answer here should be something more interesting than just "a deeper hole". Possible answers include: An elemental maelstrom, a
gate to a hostile plane, a geothermal tap that goes all the way to the magma beneath the mantle, or the maw of the world serpent.
Secondly, why is the entire compound structured so that each quadrant can only be accessed from other quadrants via the bridge? Did the complex previously serve as some sort of prison where access had to be tightly controlled (rooms 75-84 really do look like a cellblock)?Was the compound occupied by nearly incompatible, but allied racial/religious factions who needed to be kept seperate? Or were there other reasons?
If this separation was (or remains) so essential then how is burrowing between quadrants discouraged and what prevents occupants from flying across the bridge chamber?
Mulling this over my own answers would be:
The compound is a combination prison and laboratory, with the prisoners who are housed in the the west quadrant cellblock area of 74-84 being periodically hauled across the bridge to serve as subjects for cruel fantasy magic experimentation in the east quadrant of rooms 128-145. The "sensitive data" or other fruits of this experimentation are further studied and kept secure in the southern quadrant.
The prisoners and lower-level magical research technicians are kept from burrowing out by the simple expedients of denying picks and shovels in those areas, and a combination of declawing and manacling prisoners with racial burrowing abilities. Although some of the guards should have tremorsense to be able to attempt any rescue mission that tries to burrow in.
Flight across the chasm is discouraged by making sure the guards on all four entry points are quite skilled with crossbows (or other ranged attacks) and probably having a ballista or fancy-pants-blasty staff in the central rotating platform.
The pit itself is a disturbingly deep hole, with the edges coated with permenancied
grease, and it contains the remains of prior experimentation subjects - who have either become monsterous themselves or are food for some sort of nasty carrion beast or undead horror.
The adventure is that the PCs are hired to save one of the prisoners who comes from nobility, and the adventure is to get him out before the experimentation has gone to far. They can save the other prisoners if they want, and may gain additional rewards and acclaim for doing so, but some of the prisoners have already been corrupted in some way by the experimentation.
The dungeon will have guards for the prisoners and the enemy will co-ordinate a response if they realize that the PC team is assualting, but the dungeon also has a fair number of support staff and arcane studies types, whose action are limited to: flee, surrender, sound alarm, or ask to be rescued themselves.
For a 7th level adventure, this sort of dungeon would most likely be run by one of the following as the "boss monster", and that will color the majority of the rest of the inhabitants:
- A Drow arcanist trying to advance their standing within their house. (lotsa drow, spiders, driders, constructs, undead and bugs)
- A cult of Yuan-Ti (yuan-ti, other monstrous humanoids and anything even vaguely snakelike)
- One or more Mind Flayers (a motly assortment of charmed minions, with Umber Hulks as heavies, grimlock slave labor and some of the odder abberations in dark corners)
- A nest of Spirt Nagas (a tribe of evil humanoids and their pets whose chieftains are enthralled via Charming Gaze.)
"But transportation issues are social-justice issues. The toll of bad transit policies and worse infrastructure—trains and buses that don’t run well and badly serve low-income neighborhoods, vehicular traffic that pollutes the environment and endangers the lives of cyclists and pedestrians—is borne disproportionately by black and brown communities."