Here is a guide to the Gilded Age mansions on 5th Avenue, both those still standing and those lost.
Gilded Age Fifth Avenue Millionaire's Row
Fifth Avenue Gilded Age Mansions Walking Tour - Tinggly
A guide to the Gilded Age mansions of 5th Avenue's millionaire row
Manhattan Boutique Real Estate on LinkedIn: Manhattan's Trophy
A Couple of Swells - Wikipedia
Manhattan's last intact Gilded Age mansion can be yours for $50M
NYC: Fifth Ave Gilded Age Mansions Guided Walking Tour
The last “vulgar” survivor of a row of four Fifth Avenue mansions
Vanderbilt Triple Palace - Wikipedia
James Tissot and Two Ladies of Leisure
Then and Now: Millionaire's Row Mansions of Fifth Avenue