Fellow Union Terminal aficionado here. Also highly recommend to any art deco architecture lovers.

Even if you're not into art deco architecture it's worth a visit. The Omnimax theatre is worth the trip alone, but the museums are great too.

@macintux - It's hard to get on the tour because they sell out, and they don't allow photography, but the high steel tour, which includes walking up to the top of the inside of the half dome, is great. There's some duplication with the behind the scenes tour but it's still worth it. It's probably second to the (now discontinued for liability reasons) Cincinnati subway tour in terms of seeing cool hidden stuff in the Cincinnati area.