This is the Lambertville Outlet Lock.  It was built to allow canal boats to pass between the NJ and PA Delaware Canals.  They’d bring their cargo down the PA side then cross the Delaware River while attached to a cable.  It was abandoned in the early 1900s and now nature has thoroughly taken it over.  I love the way the setting sun illumines the old walls and gives the place a timeless quality.  It made this scene a joy to paint!