What can you do inside the CN tower?

The main thing is "be in the CN tower". It's quite tall, and you can ride an elevator up to the round disk part, which contains a restaurant, and get a pretty good view of the city. There's another elevator that goes up to an even higher observation deck at the base of the radio antenna.

In addition to the "wow, I'm way up here" and "wow, I'm way up here and eating too" attractions, there's a 3D movie theater, and a "motion theatre ride"... you know, the sort where your seat moves around as you watch a movie. I think these technically may be at the tower rather than in the tower; I believe they're underground at the base, though it's been a while since I've been there and I'm not positive about that.