You have to go east of Mahogany Town then go through the Ice Cave. When you come out of the Ice Cave, go south to Blackthorn City.
Go through Ice cave from mahogany town
go to blackthorn city and press a on the weird looking tree
If you are talking about the Dragon's Den in Blackthorn city,then you have to use the moves Surf and Whirlpool to get across. Then you can talk to the Elder.
Surf up the Blackthorn gym and you will be in a cave. use whirpool to get across on the left side of the cave.
you dont you battle mewtwo and get out
The last city in the Johto region is Blackthorn City. To get there, you must travel east from Mahogany Town. From there, you will see a cave (The Ice Path) in which you must go through to get there.
How do you get through ice path in pokemon SOULSILVER?
you don't go that way, instead you go though dark cave (you need rock smash) to reach blackthorn city
first go and beat team rocket in goldenrod city. once you do that head back to mahogany and head right. go through the ice cave to show up in blackthorn city
You buy a couple of repels (optional). Get through the cave. Sorry I don't know how
im not too positive about this answer but im pretty sure you cant get to blackthorn city through the dark cave
There is no Unknown Cave!!