According to the Village of Ossining Downtown Walking Tour:

The Ossining Weir Chamber, located on the Ann Street side of the Double Arch Bridge promenade, is one of six such structures located along the Old Croton Aqueduct. The purpose of the weir chambers was to regulate the flow of water along the aqueduct tunnel, allowing water to be emptied into local waterways in the event of flooding or when needed for maintenance and repair of the tunnel. The weir chambers also served as ventilators for the aqueduct system. Inside the weir chamber is a large iron sluice gate, the opening of which allowed water to drain out of the tunnel into the Sing Sing Kill below. When all of the weir chambers were opened, the entire aqueduct could be drained in just two hours. Today, the Ossining Weir Chamber is a component of the Old Croton Aqueduct State Historic Park. The organization “Friends of the Croton Aqueduct” conducts periodic tours of the Weir Chambers for the public, granting interested parties access to the inside of the weir chamber and aqueduct tunnel.

The Old Croton Aqueduct Trail is an off road footpath located directly above the water tunnel of the same name. The trail becomes the Promenade at its intersection with the Double Arch Bridge near downtown Ossining. North of downtown, the trail continues north through a wooded landscape, passing by the Gothic Revival-style Kane House before intersecting with Highland Avenue and continuing into Croton-on-Hudson. Please see the Village of Ossining Significant Sites and Structures Guide for further information on the Kane House.

Taken with a Sony RX-100 M3.