Aleph One doesn't support the changing of rooms yet. If you want to go to the other rooms, you can download the Myth II demo from http://www.getmyth.com/ and log on with that.
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Our friends with three eyes and their toys and their cyborg pets and their computers.
Those other rooms are for Myth games. I think some time back Marathon and Myth players were able to be in the same rooms but there was some confusion and the Marathon players thought the Myth players weren't suppose to be there. Well that's how I heard it long ago.
I think there are two rooms for marathon, arrival and another one with an strange name, longer then arrival. So I think it's strange you can't change rooms. Is there no prefences screen to change it?
I don't think there is... I seem to recall a mention of "edit the room setting and then re-compile" or something like that. We'd need Treelama to chime in to be sure.