Q:
Can't get into Griffonhook Run
A:
To the right of the gate there’s a dome structure with a hole in the roof. Go in there. You’re likely to have camera issues if you have a larger character, so keep jigging around and aim for pale purple.
Make sure you set your particular traits to mitigate falling damage. Even doing this puzzle correctly, you will have to take some nasty falls, so be prepared.
Another tip: Unequip your armor, you’ll save a lot in repair costs.
Its not in the building, its next to it (north) covered in seaweed.
Go a little more north and look for a section of seaweed next to the building as it covers a tunnel.