I’ve never actually played or run a game in Undermountain (although I’ve wanted to use Skullport from level 3 South for many years), but when I moved into my new place, I put the maps from the original boxed set up on my walls as “inspiration”. However, the other night I was looking up at the eastern side of level 1 and noted a few hallways that got my attention.
Quasqueton in Undermountain
There it is, my favourite published dungeon of all time (Quasqueton, the dungeon of module B1 – In Search of the Unknown), buried in the depths of undermountain. The map has been simplified significantly, but the distinct corridor shapes have been retained. Like I said in my original post about Quasqueton, I love that this dungeon can be transplanted anywhere as published.
Dyson's Dodecahedron 
I wonder how many other classic dungeons are hidden in Undermountain. Great find!
Nice catch! It’s fun spotting easter eggs in RPG products, like the EGG in Barrier Peaks or the Marvel superheroes reference in the D1-D2 compilation.
That’s pretty cool…..B-1 In search of the Unknown…..has always been my favorite dungeon as well.
I spotted this back in the 90’s, soon after this came out. I managed to get an email to Greenwood and asked him about it. His reply was that when they put the box set together, they just grabbed a bunch of maps from old modules and connected them together to make the maps. Apparently they were behind schedule and just needed to throw something together and get it on the shelf. It all started from a campaign he ran with his friends, but he never made a full set of maps. Keep looking around, as there are several other old module maps used in it. Still my favorite setting to this day and my best memories of gaming. We started every session by playing Unforgiven off the Metallica black album, still can’t hear it without immediately thinking about Undermountain.
Neat. Do you know what other maps they use to this?
This blog shows more of the maps they used: http://unvisiblecitadel.blogspot.com/2020/06/undermountain-map-origins.html
This is a very cool idea to use this module as a start campaign. Drop in Undermountain classical dungeons to fill the intentioned blanks in this module and in deeper levels. Much better than the canon 5e version.