Chicago has a population of 2.9 million and is the third largest city in the United States, with its metropolitan area home to 9.8 million inhabitants. The downtown area is dominated by skyscrapers and features wide, clean streets and good public transportation. It is a major port city on Lake Michigan known for iconic buildings like the Sears Tower, the tallest building in the U.S. at 110 stories, and the John Hancock Center, which has observation decks high above the city.