I do that Bike the Drive ride on Lake Shore Drive here in Chicago every year, so long as I'm in town. Once a year they clear the road for a few hours on a Sunday morning. You start and end at Buckingham Fountain downtown in Grant Park. From there you have your choice of two 15 mile routes---one north to the end of the Drive, the other south to the Museum of Science and Industry in Hyde Park---or one 30 mile route. Of course, no one will stop you if you decide to do it all again and shoot for 45 or 60 miles. It's a great deal of fun.

http://www.bikethedrive.org/