IMG I have used (Oh this sounds bad!) basic hydraulics to open huge doors.
Pinced directly from Archemedies(sic) using a large copper alter connected to
water filled pipes. Air in copper alter expands, pushes water into counterweight
buckets...doors open! Alter cools, air contracts sucking water back...doors
close!
Probably easier to use a gnome bound into the door or Sven the Strong.
Could be a leftover from grander times...
Non-magical is probably best, less to go wrong! (Whoops! there goes the
gnome!)
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