Keep looking, you'll find it!!!
7island
To get into the Unknown Cave you'll have to beat the Elite Four. Mewtwo will be at the end of the path. I'm pretty sure you'll also need a Pokemon with surf.
Cerulean Cave
You can't do anything with altering cave unless you have an E Reader.
Get a tutorial on you tube
the unknown M is in the rixy chamber
7island
To get into the Unknown Cave you'll have to beat the Elite Four. Mewtwo will be at the end of the path. I'm pretty sure you'll also need a Pokemon with surf.
Unknown Dungeon was the name of a cave in Red, Blue and Yellow version that is located northwest of Cerulean City you would need Surf to reach their the cave is now called Cerulean Cave.
Yes Cerulean cave is Unknown Dungeon. In Red/Blue/Yellow it was Unknown dungeon. they just changed the name in firered and leafgreen because it was near cerulean city or something. hope this helps!
Firered don't have a "solar cave"
he is on the even island in the cave named Rixy chamber
what the pooperscoopers is the unknown dungeon in Pokemon firered you dummies?!
There is no Unknown Cave!!
mewtwo is in mystery cave :D
Unknown in the cave Is all Around The Cave Near Slocan Town By:Ethan
It is in Cerulean Cave. It is on the bottom floor of the cave! :P