In my 5e game this is a junkyard/dump that lies at the bottom of an enormous pit located in the Vast, north of Raven's Bluff in Faerun. The party must use a system of ventilation pipes to make their way down until they reach the NW corner of the map, being careful not to get caught up in the fan at the end of the pipe. When they exit the pipe they meet a resident "custodian" of sorts who is clearly senile and who uses a broom and endless hours of sweeping to keep the place tidy. They must rescue the dump owner's pet cat, who they mistakenly believe to be the dump owner's daughter due to some intentionally obtuse communication ("Please rescue my little girl!!!!" etc.). The fact that it's a cat isn't revealed until they've battled their way through some rust monsters and maybe a troll or some type of hag who can cast animate objects to use the junk in combat. Lots of possibilities. The party is rewarded for saving the cat with one piece of a legendary weapon that appears to be, well, junk without the other parts, which they are likely to find later as the quest goes on.