Nice, this makes me even more pumped for Witcher 3. :D

The Valak Mountain in Xenoblade Chronicles 1 is amazing.

Freezeezy Peak - Banjo Kazooie, mostly because of the music but also because I never played any other level that was able to hype me up for christmas more than this one.

Phendrana Rifts - Metroid Prime, excellent music, but also nice visual design. You could almost see and feel how cold it is.

5-4 Frosty Fruits - Donkey Kong Country Tropical Freeze, because this is the first ice level in the game and the first time that we see why the enemies captured all the fruits, to turn them into giant popsicles. It's brilliant. Also because it features an amazing remix of one of the best tracks in the entire DKC series.

5-6 Up Shuttlethread Pass - Yoshi's Woolly World, mostly because of the peaceful and heart warming music. This level makes me want to sit next to a fireplace with a cup of steaming hot cocoa.

Snowpeak Ruins - Twilight Princess, one of the most bizarre yet creative dungeons in the entire series in my opinion.

Tundra Man stage - Mega Man 11, very cool stage.

Chill Penguin stage - Mega Man X, usually the first stage I play whenever I play this game because of the essential slide upgrade.

Ice Country - Secret of Mana, once again a wonderful music. This is the song that first comes to mind when I nostalgically think about this game.

The Mountain - Journey. This part of the game made me cry.

Whoever said Phendrana Drifts from Metroid Prime, I second that. Quite the contrast to exploring Magmoor Caverns as well. And I could be wrong, but one of the main memories I have of that game is going through the lab that gets all dark after you find the visor upgrade, and then you have to make your way out while getting attacked by space pirates. The part I could be wrong about is that I think it's accessed from within Phendrana. I picture it on a bridge way up high with rooms in all directions, one of them being the entrance to this lab.

Whole Northern region of Gothic 3 (Nordmar)

Painted World of Ariandel (Dark souls 3)

HZD:TFW (DLC)

Gives me chillz.

How is the most beautiful and best ice track ever not mentioned...

Rise of the Tomb Raider has some great snow levels. Forza Horizon 4 during the winter season is really fun to drive around in! 

Oh wait yeah I might have to change my answer to Ice Cap Zone and HZD: Frozen Wild dlc being tied. Sonic 3 has too much nostalgic love in my heart to put in 2nd hahah

There are many that I have enjoyed throughout the ages. However my favorite will always be Mario 64's Cool, Cool Mountain. First, in 1996 I was 12. Second, I had lived in a tropical Island all of my life and Snow seemed alien and wondrous to me. And 3rd, Mario 64 was the first proper 3-D game that I had played at that point.

It was a magical and endearing experience. The slide was addictive as heck and diving head first into the snow with Mario was an unforgettable experience.