The Wrigley Building glows as white as the Doublemint Twins’ teeth, day or night. Chewing-gum guy William Wrigley built it that way on purpose, because he wanted it to be attention-grabbing like a billboard. More than 250,000 glazed terra-cotta tiles make up the facade; a computer database tracks each one and indicates when it needs to be cleaned and polished.

Banks of megawatt lamps on the river’s southern side light up the tiles each night.