Formerly the Guggenheim estate, this preserve covers forest and a beautiful bayfront beach (that is closed to all visitation except nature tours); the visitor center is in the Onondaga limestone Castle Gould, built in the 19th century by railroad heir Howard Gould. Visitors can also tour the 1923 mansion Falaise, one of the few intact and furnished mansions from that era; and the Hempstead House, a 1912 Tudor-style castle (by appointment).
Guided nature walks take place on the second Sunday of every month.