Tidal Basin

This guide to the Tidal Basin in Washington, D.C. begins with the flood of February 1881, when water swallowed the southern edge of the city so completely that people got around only by boat. It follows the engineers Congress sent to reclaim the marshy Potomac Flats, penning part of the river inside a stone-walled basin whose gates once let two hundred fifty million gallons pour in and out twice a day. Look down at the grass near the water's edge and you may find river snails stranded on dry land.