Firered don't have a "solar cave"
You can get Mewtwo in the Cerulean Cave.
altering cave,
in the land cave.
Cerulean Cave
bartonvilleType your answer here...
You can't
mewtwo is in mystery cave :D
The only dark type Pokemon you can get in firered is murkrow which happens to be in lost cave on five island.
icefall cave
icefall cave firered only
in the yellow area