The Charles River Basin was transformed between 1903 and 1910 by a dam system that replaced tidal mudflats with a controlled freshwater reservoir, creating the nine-mile urban waterway that defines Boston's geography today. What had been an industrial corridor became a recreational artery bordered by the Esplanade on the Boston side and Memorial Drive on the Cambridge bank, with eight historic bridges spanning the river between the Museum of Science and the Eliot Bridge. The Longfellow Bridge, completed in 1906, carries both automobile traffic and the MBTA Red Line over granite piers that earned it the nickname "Salt and Pepper Bridge" from Boston residents. Boston Charles River sightseeing cruise departures operate from CambridgeSide, a location that positions passengers at the eastern terminus of the navigable basin. Narrated tours travel west past MIT's riverside campus, the Harvard rowing houses, and the gold dome of the Massachusetts State House visible across the basin. The riverbanks hold over a century of collegiate rowing history — Harvard and MIT crews still train in the same waters where the first intercollegiate regatta was held in 1852. Boston University's stone boathouses line the southern shore, and the Hatch Shell amphitheater, built in 1940, remains the site of the Boston Pops' Fourth of July concerts. The cruise route passes beneath the Massachusetts Avenue Bridge, where engineering students measure the span in "Smoots" — a unit created in 1958 when fraternity pledge Oliver Smoot was laid end-to-end across the bridge 364.4 times. The basin's width varies from 200 to 2,000 feet, and the controlled water level allows year-round navigation without tidal scheduling. Boston Charles River sightseeing cruise tours provide perspectives on Beacon Hill's Federal-era brick rowhouses, the contemporary glass towers of Kendall Square, and the Back Bay skyline that cannot be captured from street level. The river divides two cities but functions as a shared public space, bordered by 17 miles of parkland managed by the Department of Conservation and Recreation since the basin's completion.