Muttontown is nice, but I do not think this photo is of it as there are eroded steps but no railing there. Here are some comparison photos of Muttontown http://clydesguides.blogspot.com/2010/12/knollwood-estate-muttontown-long-island.html To get to Vanderbilt http://www.vanderbiltmuseum.org/address-directions/ if you google map it you will see where the round pool is in the back of the estate