Although construction began on William K. Vanderbilt II's exquisite Spanish Revival mansion in 1910, the home wasn't completed until some 26 years later. Rooms in the Gold Coast-era mansion are now open to the public, allowing intimate glimpses into the lifestyle of one of the nation's wealthiest families. Aside from the historic Vanderbilt Mansion, the museum complex covers 43 acres and features the curator's cottage, seaplane hangar, boathouse, gardens, and fountains. Visitors are also encouraged to visit the estate's maritime and natural history museums and the planetarium, which opened in 1971.