On island 7, where the double battle trainers are.
The boulder puzzle can be found in Sevault Canyon on Quest Island. The puzzle itself is inside a chamber called Tanoby Key. Tanoby Key is found in a cave near the north of the Canyon.
On seven island near tanoby chambers.
in union cave you need to go down the ladder by the scientist, surf in the water and look in that cave till you find a boulder. move it and exit the cave, hop down the ledge and into the other cave. there you have it!
The Treasure Cave is in Mountain Falls Which is Hidden Behind a Giant Boulder. You Will Have to Destroy the Boulder To Get In The Treasure Cave
You can move that boulder by using the hidden move strength.
The tanoby ruins consists of many different chambers inside you can find and capture the pokemon Unown but only after solving the boulder puzzle in Tanoby Key which is a cave not to far from the ruins.
Once you finish the boulder puzzle in the cave called Tanoby Key on Seven Island enter the Tanoby Chambers and walk around eventually a Wild Unown will appear.
its not under a boulder its smeargle and there everywhere in artisan cave.
He used a boulder.
in the cave with big boulder
there is a mission you need to do
Once you have finished the boulder puzzle in Tanoby Key which is a cave located on Seven Island you can find the pokemon Unown inside the Tanoby Chambers just walk around for a bit and you will find one.