You'll think you've died and gone to medieval Europe at this place. The castles on the grounds are a stunning display of extravagance and wealth from a different era. Created by Howard Gould -- son of railroad tycoon Jay Gould -- the 100,000-square-foot 1904 castle (Castle Gould) and 1912 Tudor-style manor (Hempstead House; residence of second owner, Daniel Guggenheim) sit on gorgeous property. Unfortunately, due to renovations and recent administrative changes, those buildings may not be open. But also on the grounds is the beautiful Falaise, a Normandy-style manor house decked out in period furnishings, which was built by Harry F. Guggenheim in 1923.
The preserve is full of nature trails; bring a picnic lunch (you can't miss with a sandwich from Best Bagels, 40 Middle Neck Rd., Great Neck; tel. 516/482-9860) and make a day of it.