The Old Croton Aqueduct, New York City’s original water supply, runs from, Croton-on-Hudson into the Bronx and Manhattan, passing through Sleepy Hollow and Tarrytown. For most of its length, the Aqueduct is a horseshoe-shaped brick tunnel 8.5 feet high by 7.5 feet wide, set on a stone foundation and protected with an earthen cover and stone facing at embankment walls. Don’t miss this rare chance to enter one of the historic water diversion chamber to view the tunnel itself!