The John Hancock Center at Chicago.

The most impressive building we have seen passing Gold Coast of Chicago, is the giant John Hancock Center, 1127 ft tall which has a great 94th-floor observatory that's often less crowded than the one at Sears Tower, besides the views of the Loop and Lake Michigan are superior here. As a tip, we skiped the observatory once and took the 96th floor Signature Lounge, where the views are free if we buy drinks. The building is at 875 N Michigan Ave, open from 9 am to 11 pm, the entrance costs about 9 $.