A classic Finnish comedy movie (English title The Cold Old Days, literally the title just means "snow castle"), produced by VEK (Jukka Virtanen, Aarre Elo, Matti Kuusla), in 1965. Won the Montreaux Golden Rose award.
The story? Three people - "restaurers" - go to a castle that has all sorts of population that shouldn't be there. Like a bunch of medieval soldiers.
The most memorable scene is, of course, the staircase scene. One of the restaurers walk up stairs (with appropriate music, of course, need to check name of this music piece too), with only the floor number changing on the wall - and as he walks up, more and more soldiers with halberds walk behind him. As he gets to the top and goes down the corridor, he notices he's being followed (music stops), and he turns - only to find empty corridor - and keeps walking while looking back. All the soldiers are walking in front of him...
(No information about the actors and other makers available on the web - I need to consult the literature...)