Here's an absolutely gorgeous Doom map called Lullaby

Lullaby is a sprawling, beautiful map for Doom 2 that puts the level and visual design of many full-fledged, expensive games to shame. Created by mapper-modder Danlex for Doom port GZDoom, it's a testament to the game design talents that lay deep in the communities of modders and mappers for old games. 

Lullaby does shocking things if you know the constraints of the original Doom engine, and it does them well. It's a very technically focused creation, with a lot of emphasis put on how it looks, the aesthetic, sense of place, and surreal, dream-like nature of the environment. It's not too ultra-hard, even, so if you want to go at it as a Doom novice that's perfectly fine. It takes about an hour to play through.

You can find the map on the Doomworld forums, and modder Danlex on Twitter.