You have to go to the S.S Anne which will drop you off at Vermillion.
Then you will see (to the right of it) there is a massive Pokemon blocking the way to a cave. That is diglett's cave.
To get into it, you have to tune your pokegear radio to Poke Flute and it will wake up the Snorlax and attack you. All you need then is to either beat it or capture it (probably the best option as its not going to appear again) and then it will leave you with the entrance to Diglett's Cave.
Chat with our AI personalities
In crystal it is to the right of vermillion city, which is the place you arrive when you get off the S.S Anne. To get to it, you have to awaken the massive Pokemon blocking the way (Snorlax) by switching on your Pokegear and tuning it to 'Pokemon Sleep' or something like that. Then if you click on the Pokemon it will wake up and battle you. Then catch it or defeat it, and you will be able to get into diglett's cave.
Digletts are the only Pokemon in Diglett's cave but they appear so often that when you take your first step into the cave that there is a 7 out of nine chance a Diglett will appear
You can not obtain a Crystal Onix in the Pokemon games. It is only featured in the TV show Pokemon
you have to get the poke flute poke gear radio station and play it next to snorelax
I have no crystal. I think in crystal cave? Dont work? Watch on joutube.by by from belgium.