The country's third-largest city, Chicago has a totally different vibe from the big cities on either coast. Nicknamed "Paris on the Prairie" because of its wide boulevards and tree-shaded parks, Chicago has a lot in common with that European capital. It has world-class museums, a breathtaking array of restaurants and gay nightlife that rivals any of its neighbors. This sophisticated city was home to the world's first skyscraper. (That was 1885, and the Home Insurance Building was just nine stories tall.) Since then, the city has attracted famous architects like Louis Sullivan and Mies van der Rohe. The skyline's main feature these days is the iconic Willis Tower, the former Sears Tower.   Getting her...