3 Riverside Drive

The Philip and Maria Kleeberg House is a stunning, unique and impossibly grand 11,000-square-foot manse overlooking the Hudson River at 3 Riverside Drive. This 19th-century limestone landmark was designed by noted mansion architect C.P.H. Gilbert for the aforementioned wealthy pair. Young Mr. K was something of what today we’d call a serial tech entrepreneur, and the mansion sits on a stretch of the Hudson River that was being developed to rival the grandeur of Fifth Avenue. According to a New York Times article in 2012–when the 18-room home hit the market at $40 million–the home’s current owners, Regina Kislin, a real estate developer, and her husband, photographer Anatoly Siyagine, found it in 1995 in a state of disrepair, bought it for $10 million and embarked on a facelift of epic proportions based on the potential they saw in the regal wreck, which Ms. Kislin says "...reminded my husband of the mansions in St. Petersburg back in Russia.” According to the current listing, "It is as close as a Manhattanite can come to living in a European castle." Several price chops later at $20 million (h/t TRD), it remains a pretty incredible piece of real estate, albeit with a more realistic price tag. In addition to the restoration efforts, modern touches include an elevator and an indoor pool, sauna and gym in the cellar.
Must be seen to be believed, this way