This incredible $16-million Lenox Hill townhouse, originally built in 1899, has a two-story glass-enclosed atrium that leads to a gorgeous ground floor planted garden. But one of the most exotic exterior details in this palatial dream home--which was also this year's Kips Bay Decorator Show House--is the outdoor bathtub on a (hopefully) private fifth-floor terrace.

Whether you're in your bathing suit or your birthday suit, soaking al fresco is a thrill that everyone should experience at least once and an outdoor tub in NYC is a rare luxury indeed.

Real Estate Want is a weekly column featuring New York City apartment details we're coveting right now.