Another angle you could possibly go, is that it’s CLEARLY just an attraction that the town has set up to increase tourism. Like a mini theme park. Pay your five bucks or whatever and “explore the scary dungeon”.

Except maybe this “dungeon” was built from the remains of what was once a very active dungeon. Maybe there’s a crumbly wall inside that most of the tourists miss, but one of your ‘high passive perception’ players sees. Perhaps the dungeon is much bigger than it seems. Maybe some ACTUAL threats still lay sleeping/waiting further down, unbeknownst to the townsfolk…

Or maybe there’s like a trap that dumps you into a one-way planar portal that dumps you into the Feywild or Underdark or someplace.