This tiny steel cottage perched on a rock pile is the smallest house ever built on Riverside Drive

Ever since it officially opened in 1880, Riverside Drive has promised bigness: spacious lots, roomy mansions, and towering prewar apartment houses with expansive views across the Hudson River. So how did this one-story stub of a house end up on the south corner of Riverside Drive and West 107th Street, nestled snugly among its neighbors and perched on top of a leftover pile of Manhattan schist? It doesn’t have the grandeur of the prewar apartment building behind it, nor does it feature the stylish bow front of the row house it sits against, which was completed in the early 1900s. And it’s got nothing on the French Renaissance masterpiece (third image) across the street. Built in 1909 for Turkish tobacco magnate Morris Schinasi, this magnificent palace is one of only two remaining free-standing mansions built during Riverside Drive’s Gilded Age heyday. But the little house was indeed a real house, with an actual address at 328 West 107th Street. And its short-lived presence on the…