One of the best views in downtown Chicago is from The Terrace at Trump Tower, and it's only 16 floors up. In every direction there are amazing architectural treasures; The Wrigley Building clock tower and the Tribune Tower's flying buttresses to name two, and a fabulous view of the Chicago River and Lake Michigan. It's really dramatic and impressive. Drinks are a little pricey but worth it for the ambiance, I think. We didn't have food, or even look at the menu so I can't comment although other people seemed to be enjoying what they were eating.
It's a fabulous place to have a summer cocktail and take in the Chicago landscape. And on Wednesdays and Saturdays you'd also be able to enjoy the fireworks at Navy Pier.