Best Video Game Levels

Ok, so as a quzi followup to my best SNES games, I add a new discussion. What are the greatest video game levels of all time?

I will list some in no particular order:

Casino Night from Sonic 2
1-1 and 1-3 from Super Mario Brothers 3
Lavos battles at end of Chrono Trigger
First Dungeon in Legend of Zelda-the original (Steve)
Mine Carts from Donkey Kong Country (Specific name I do not remember)
D-Day from Allied Assault
Facing Worlds from Unreal Tournament (Derek)
The Hunter's Map from StarCraft (Steve)
Castle 4 of Super Mario Brothers (Derek)
A6 of Bubble Bobble (Derek)
The Overlord final battle from StarCraft (Derek)
Altered Beast first level (Steve)
Last race in the Mushroom Cup of Super Mario Kart (Derek)
Colossus 1 in Shadow of the Colossus (Steve)

Add more that you can think of!