which 1 is that?
is the same one in his ending? if so, that's the lava shrine

If you mean the swamp arena, it wasn't put in as a playable stage.

Yeh swamp arena.......dont u hate people who make shit up.....thanks guys for covering that didnt want to go through the stress thinking i could UNLOCK RAIN......some liar said that opening "RA"
and "IN" in the krypt unlocked RAIN.....that pisses me off when i knew it wasnt true.
cheers again guys

it's in the gba version. and rain is in the game. unlock koffin YA, start a vs battle and pick subzero as the first character (select him with X)
and theond one also subzero (select him with start). He has his u move where he freezes them with a bubble.