Where is the Fortress of Solitude anyway? Is it actually built on Canadian (or Norwegian or Russian) soil, or directly on the ice? If the latter, how? Is it more like a drifting ice station, or what? Artctic ice isn't permanent. Do submarines occasionally surface in Superman's front yard?
Or is it in the Antarctic again? Probably not in one of those lesser-liked locales, like the Andes or that glowly tesseract thing.
Also, does it bug anyone else when they show the Titanic in the Fortress? If he raised it, rebuilt it, that's okay, I suppose, but it's seems odd that he would put that in a private collection in a big room instead of setting it up as, say, a museum ship in Metropolis harbor so people and researchers could look at it. I don't think even James Cameron would keep the Titanic in his house.