Today I went up Terra Tower (all the way up to the point where you go and fight the Lunar Dragon.), and I remember entering a room that brought me to, of all places, the upper left tower of Viper Manor, where as you remember, Belthasar's there along with the "ghosts" of young Crono, Marle, and Lucca, where you're told more about Chronopolis vs. Dinopolis. And then they all disappear (well, the ghosts do at least. I'm not sure about Belthasar...). Once you're back in Terra Tower, if you try to go back there, it changes into the correct path up the tower again.
Are there any theories on this? I did a search and couldn't find anything, and it's been bugging me ever since I saw it (at first I thought it was FATE, but then I remembered Fate was dead so...)