An Old Westbury mansion that was built by famed architect Thomas Hastings for himself in the early 1900s is on the market for $12 million.

The 10-bedroom Georgian Colonial is filled with antique details, including plaster ceilings, marble floors and classic moldings. The home also has an elevator and the 4.3-acre property features three cottages.

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Hastings designed such iconic buildings as the New York Public Library with the firm Carrère and Hastings, which he formed with John Merven Carrère in 1885.

The property is listed with Joan Valenti of Coldwell Banker Residential.