[Ironhawk]

You might consider going to Cleveland, even without a car? I'm sure there must be a bus route or somesuch from Columbus to there. Its a decent city at any rate and it is right on one of the Great Lakes... Lake Erie, I believe? Worth seeing.

If you don't get to the States often tho, and you have the time, I do suggest that you rent a car and go to Niagra Falls. It's probably about the most interesting natural feature in that area. Mapquest says its about a day's drive from Columbus to Niagra Falls. You could even split that up by driving to Cleveland, spending some time there and then continuing on to Niagra?