Columbus native here. COSI (science museum) is nice but pretty spendy if you're not a member, and I don't think way more impressive than anywhere else. The zoo is nice. There are lots of metro parks that can be visited for free, rivers to walk along, interesting dining at all price points, if you are so lucky to be here on a first Friday there is Gallery Hop where all the art galleries in the Short North open up their doors in the evening--or visit the Short North during the day and see the galleries then. German Village is worth a walkabout. There are places downtown that you can rent a bike and tool around. I think it's funny that Easton Town Center came up first on that touristy list... I can't stand Easton, it's basically a giant monument to consumerism. Going on vacation to go shopping is not my idea of fun (or, I bet, yours either, since you posted on this board).