Joe, you should definitely check out Grant
(the one with buckingham fountain) and Millennium
(the one with the cloudgate sculpture aka 'bean') Parks which are adjacent to one another between Michigan Ave & the lakefront. If you want to hit one of the observation decks, most people find the John Hancock bldg deck to be a better experience than the Sears Tower, even though it's not quite as tall. I believe there is even some kind of bar slash restaurant type thing at the top of John Hancock too, so you might look into that. The parks are surrounded by Field Museum
and Shedd Aquarium
(to the south end) and the Art Institute
(in the middle).
As far as new architecture construction goes, you will find a new big one(One Museum Park
) on the south end of Grant Park... it's the tallest thing around.. you can't miss it. That one is not quite topped out yet, but it's quite a sight. In a few years that whole area is going to be built up very tall and extend the skyline south. http://www.onemuseumpark.com/home.html
If you find yourself near the mouth of the Chicago River(near Navy Pier) you can spot the newly founded construction site for the Chicago Spire
which will be the tallest building in the US @ 2,000 feet(blowing the Freedom Tower out of the water) and the tallest all residential
building in the world. The site is immediately west of Lake Shore Drive on the north bank of the river. Right now they're just drilling caissons and preparing for the new roadways so there isn't a lot to see, but it's amazing to visualize the massive structure that will exist on such a tiny plot in a few short years. IMO this is the single most exciting(and gorgeous) project in the world right now... just check out the official website: http://www.thechicagospire.com
If you continue west up the river you'll find the new Trump building
right on the little kink in the river on the north bank. This one's about half way up right now, and should look amazing when completed roughly the same height as John Hancock and the AON building. Looking west directly down the river you can already see what an amazing location this building has. http://www.trumpchicago.com/main.htm Waterview Tower
is further west along the river on the south bank of the river on Clark Street. Another 1000+ footer. http://www.waterviewtower.com/300N. LaSalle
is across the other side of the river from Waterview and should be very nice when completed as well.
One of the coolest ways to view some of the amazing architecture, new AND old, is to take the architectural river boat tour if you have time.