Procedural generation is an interesting topic to me, as it forgoes traditional level design in favor of a bunch of formulas, rules, and random elements to make varied replayable gameplay.
One of my favorite procgen games is Dwarf Fortress, and how it creates a fully realized world with lore and history, and then places both fortress and adventures as relatively small stories in said world.
Also Deep rock galactic is great in varying its caves, from normal tunnels to massive caverns that you can only traverse using ziplines and platforms
I've had a lot of fun playing Descenders. It's not usually my type of game but the way that the levels are constantly changing, but not so much that's it's completely different, is really cool to me! and keeps it interesting and challenging.