Old wife's tale says that the devil himself created this rocky formation that resembles stairs. So this place is known for people here for the name Pirunportaat - The Devil's Stairs - in Finnish.*
Even this tale it is worthwhile place to visit atleast in summertime as on a top of the stairs there is nice little park with nice scenery over the town and the Porvoo Cathedral.
* Information is from Porvoo city tourism website: free pdf brochure (page 11)