I recall seeing this swimming pool on here the other day, but I'm not sure where. I've been to this pool. It is in the basement of Biltmore Estate, of the Vanderbilt family, meaning Gloria Vanbderbilt and Anderson Cooper

Biltmore Estate is a historic house museum and tourist attraction in Asheville, North Carolina. Biltmore House, the main residence, is a Châteauesque-style mansion built for George Washington Vanderbilt II between 1889 and 1895 and is the largest privately owned house in the United States, at 178,926 square feet (16,622.8 m2) of floor space (135,280 square feet of living area).[2] Still owned by George Vanderbilt's descendants, it remains one of the most prominent examples of Gilded Age mansions.

https://en.wikipedia.org/wiki/Biltmore_Estate