It's never fully explained other than people believe in the Games he went there to get stronger.
Go to Vermilion city. After that go to the east and you will see digglet's cave. You can get to digglet's cave only in Pokemon Red, Pokemon Blue, Pokemon Yellow, Pokemon Gold ans Silver , Pokemon Crystal , Pokemon Fire Red ans Pokemon Leaf Green,
at the end of stormy cave u will find kyogre the sea basin pokemon.
The Silver Cave is located in Mt. Silver in which you can go after you get all the Johto and Kanto badges. In the Silver Cave you can find lots of strong Pokemon and fight the final boss, Red at the top of the cave.
You can't trade Pokemon from Pokemon Gold to Pokemon Red, you can only trade Pokemon from Red to Gold and not the opposite.
it is only in: red green, reb blue, yellow, fire red and leaf green, heart gold and soul silver.
After you beat the Elite Four go into Cerulean Cave and follow the maze and you WILL see Mewto standing at the end of the maze!!!
There is no altering cave in pookemon red since the sevii islands don't exist in Pokemon red only in Pokemon firered and leafgreen in six island after going past the forest and the altering cave is also in Pokemon emerald in route 103 a cave appears after beating the elite 4.
there is no ledgendery in southern cave
there is no diglett cave in Pokemon ruby only in leaf green and fire red
in Pokemon fire red and leaf green, you find him in cerulean cave, in Pokemon red blue and yellow, you find him in unknown cave (a.k.a same place in the remakes), and in Crystal, gold, silver, and their remakes, you find him in the same place as ive just explained
He is in the culean cave
You Can Go Into This Cave Once You Have Beaten The Pokemon League. Cerulean Cave Is Where Chanseys And Mewto At LVL 70.