The glass tube room is maridia in the map screen, a big hint. Also, it's not the only way into maridia.
I'm gonna 2nd ocarina of time. I've sat down to play it a number of times, and although i love the atmosphere, music, and so on, I always got really bored with it and quit. Thanks for giving me a 3d game to explore in, too bad the combat is one dimensional since z targeting removes 2 dimensions (ok, maybe not literally). It's funny how they seemed to nail 3d action right the first time with SM64, as basic as it was, the pacing and gameplay was great, and there weren't any platformers after that were quite as fun.