The Loop is Chicago's operating system — the downtown core circled by the elevated tracks that give it both name and soundtrack. Within its borders stand the buildings that constitute a timeline of American architecture: Sullivan's Carson Pirie Scott (now Sullivan Center), Mies's Federal Center, SOM's Willis Tower, and the Aqua Tower's undulating balconies. The Art Institute anchors the southern edge with a collection that competes with any on the continent.
Millennium Park occupies the northeastern corner, Cloud Gate reflecting the skyline in its polished-steel curves. The Chicago Riverwalk descends to water level along the southern bank, where kayakers and cocktail drinkers share the canyon between buildings. The Loop empties after business hours, which creates a particular melancholy — a city built for a million people populated by a few thousand night owls, the architecture performing for an audience that has gone home.
Morning is when the Loop is most itself: the commuter rush, the L screeching overhead, the coffee lines, the particular energy of a downtown that works for a living rather than posing for tourists.