D&D 5E (2014) What is your favorite encounter site or dungeon from an official module?

[Remathilis]

Mr. Dorey's warehouse from the Styes (Ghosts of Saltmarsh) the whole module is creepy and disturbing in a Lovecraftian way, but fighting skum mutants on a boat attached to a crane over a city street is so surreal and atmospheric it gave my Ravenloft players the creeps.

 

[TheSword]

I’m a big fan of Varkenbluff Museum from Keys from the Golden Vault. Evocative location with a lot going on. The Casino, Stygian Gambit, is also really good fun.

I also really enjoyed the city of Nangalore from Tomb of Annihilation and the Tomb itself.

I really enjoyed the Amber Temple in Curse of Strahd. Pretty unique location.

The product with the most great locations is Dragon Heist - chock full of great locations. Pretty much every one of the main dungeons in game are really high quality and interesting. From the first warehouse to the 4 villain’s lairs

Forge of Fury is probably one of the best adventure locations ever released for any edition I would say (I’ll be using it as the fallen kingdom of Tethyamar in my Dales Sandbox. So I wholeheartedly agree with @Zardnaar