The Celestial Castle in Valkyrie Profile is a really crappy dungeon. I can't believe that anyone making this thought it would be a good idea to kick you back to the world map after falling off a platform, wasting 2 periods in the process, and there isn't even a save point before there. Most of the hard mode-exclusive dungeons have been really good (especially the Tombs of Amenti) but this is just incredibly cheap.
eh. I think I ignored the treasures there anyways, but at least the game for the most part makes each dungeon fresh (for better or worse) in different ways. Either way, I remember me holding my head more at Lezard's giant ass tower and Amenti (because it took forever; I got lost).