On the market for sale. Again. Any architecture lover knows that black door which says 23 (in the photo below). In fact, that 1867 town house is located at 23 Beekman Place, New York City’s finest residential block. In this famed building, American architect Paul Rudolph (1918-97) made his home, by building a glass-and-steel penthouse, where he resided between 1961 and 1997, the year he died. Its iconic steel-framed cage balconies can be seen by anyone walking on this block, located in Turtle Bay. This powerful and dynamic space-age home, built as a four-story cantilevered space and designated New York City Landmark (in 2010), is so unlivable and adventurous (or ‘unhabitated’ in the words of Sylvia Lavin) that it keeps coming back to the market. This time, it is offered for $18.5 million. Equipped with a suspended transparent Lucite bathroom and surfaces in mirrored plastic laminates, and still photographed with Rudolph’s furniture, which he designed in stainless steel and plexiglas, was more recently renovated by Della Valle Bernheimer.