I have the vaguest memory of a TV show (maybe a BBC import?) in which the protagonists were moving through the sections of a massive generation ship whose inhabitants had forgotten that they were on a spaceship... I know there was an RPG with the same plot (which, after all, is a pretty great blank slate) but I definitely feel I saw this on a static-filled 13" B&W TV back in the day...
The Starlost, created by Harlan Ellison as Cordwainer Bird. I believe it was made in Canada. Ellison felt he started with a solid and wonderful concept, but that budgeting and network interference had reduced the show to something rather poor, so he invoked the clause he always required in his contracts to let him change his name on the credits to Cordwainer Bird. (That was his way of "flipping the bird" at producers that screwed up otherwise good productions.) That he "birded" the show is an flag that there were problems with the series.
The main characters were from a technologically backward environment known as Cyprus Corners and there were a number of domes (called biospheres) on the ship with bounce tubes that connected them. Walk in a bounce tube and step on the right spot and you fly to the end of the tube.
They found a projector that would display a man's face and answer some questions and found the bridge (with skeletons on it from the "accident") and learned the Earthship Ark was on a collision course for a "class G solar star." They were trying to find a way to save the Ark by steering it.
They had fled Earth due to some unspecified disaster that made it uninhabitable.
In many ways it was ahead of its time, or would have been if they had let Ellison have his way. He had planned out a rough storyline that would have them eventually saving the Ark and finding a home and finding out what had caused the accident that had killed off the main crew and left the Ark adrift. At that time, it was a new idea that a story could be told with situations changing from episode to episode.
It's a pity the producers and network squashed what could have been a ground breaking and outstanding series.
For more general information on the series, including how the execs destroyed it, this site provides some great info.
I believe that Ben Bova was also involved in this project and it had a similar theme to one of his novels. The plot got silly and the production values were just horrible. The generation ship looked like a lot of empty plastic jello cups that had been glued onto Styrofoam. Ben Bova gave up on this one as well as Harlan Ellison. (Ellison was also miffed at his "City on the Edge of Forever," Star Trek episode.