First you must beat the Elite Four. Second you must have the National Dex. After you obtain the National Dex. Go to One Island and help Bill's friend by getting the ruby and sapphire from the other islands. Then the person blocking Cerulean Cave will have left and you may enter the cave to catch Lv. 70 Mewtwo!
Go east from cerulean city keep going until you reach water go south and into the cave this is Rock Tunnel.
Go past mt moon go east and you will be in cerulean city.
You Can Go Into This Cave Once You Have Beaten The Pokemon League. Cerulean Cave Is Where Chanseys And Mewto At LVL 70.
You have to go east from Cerulean city ( where the little tree is ) and go through the cave to lavender town.
travel north from cerulean and on the trainer bridge. go left immedietly after crossing and surf south, west south and west again. there is a cave door just to the right. this is cerulean cave
go to the cerulean cave and catch mewtwo
Go to the cave between Cerulean City and Pewter City.
Beat the elite four and help celio fix the machine
go to cerulean cave after you beat the elite four and help celio fix his machine on those islands. you go into cerulean cave work your way through that and mewtwo is in there
first you have to beat Elite Four then you can use surf to get there hope that helps..
you get 60 Pokemon beat the elite 4 and go to the cerulean cave mewtwo is somewhere in there
After you beat the Elite Four.
get the complete pokedex from prof. oak. go to the sevvi islands and do missions there. get mewto in cerulean cave. complete your pokedex.
Beat the sevvi islands and the Pokemon league. Then go to Cerulean city and get to Cerulean cave. Once you're inside, navigate your way through the cave. Mewtwo is at level 70. Be sure that you are ready to give it all you got. ^_^
Go east from cerulean city keep going until you reach water go south and into the cave this is Rock Tunnel.
Go past mt moon go east and you will be in cerulean city.
You Can Go Into This Cave Once You Have Beaten The Pokemon League. Cerulean Cave Is Where Chanseys And Mewto At LVL 70.