Chicago River, South Branch

The Sears Tower, one of the world's tallest buildings, rises 110 stories above the Chicago River and its array of movable bridges. Virtually all of Chicago's bridges are trunnion bascules. "Bascule" is derived from the French word for see-saw. The bridges basically pivot on a horizontal shaft, the trunnion. The city boasts 52 movable bridges in all, which rise and fall in synchronization across the river, much to the aggravation of drivers and pedestrians who happen to be in a hurry, and to the delight of spectators, visitors and natives alike, who appreciate watching the boats pass under the bridges throughout the spring, summer, and autumn seasons.