exterior, NYIT de Seversky Mansion, Greenvale, New York

In my opinion, this is the most beautiful Gatsby era estate on Long Island's Gold Coast.  The New York Institute of Technology keeps the grounds impeccable.

The Dupont/Guest estate was built in 1916 by businessman, inventor, and philanthropist Alfred I. du Pont, who commissioned architect Thomas Hastings of Carrere & Hastings to design his new Long Island residence. Du Pont’s White Eagle, as the neoclassical/Georgian mansion situated on almost 300 acres in Old Westbury (Oyster Bay) was then called, was completed in 1918. Two years later, Mrs. du Pont, the former Alicia Bradford Maddox, died unexpectedly. After Du Pont remarried, he sold the estate in 1926 to steel magnate Fredrick E. and Amy Phipps Guest, who renamed the estate Templeton.
 
When Amy Phipps Guest’s parents gave up their 5th Ave. residence in Manhattan in 1928, she renovated her Old Westbury home. The entire marble entry hall and stairs of the 5th Ave residence was dismantled stone by stone and moved to Templeton. The newly installed grand staircase led to 13 classic European country-styled bedrooms and parlors, originally designed by Charles of London.
 
Mr. Guest, Winston Churchill’s first cousin, was the grandson of the seventh Duke of Marlborough. Mrs. Guest stayed on at the estate after her husband’s death in 1937. Upon her death in 1959, the mansion was left to her son Winston Guest, a well-known international polo player. In 1972, New York Institute of Technology purchased Templeton from the Guest family and named it after the famous Russian aviator, Alexander P. de Seversky, a member of the NYIT Board of Trustees who was instrumental in the acquisition.