Longtime reader Harald Maassen just released a really tight dungeon adventure called "Hidden Grove of the Deep Druids," which I contributed artwork for!
It's available as a Pay What You Want download on the Dungeon Master's Guild. Worry not though. It's a decently system-flexible adventure good for all medieval-ish fantasy dungeoncrawlers. If you are a 5E player, it provides some lite mechanical support to run the adventure in a more old-school way.
The premise? "Evil druid cult." An ever-elusive archetype but one that I think Harald has nailed here. If you've never used druids as villains, you should really give it a whirl.
It's a medium-sized dungeon that's non-linear, has lots and lots of dangers (especially weird fungi), and has clean and helpful formatting. It'll make a fine addition to anyone's collection of solid, vanilla-yet-tasty dungeons to slot into their game.