As more and more glass-walled, gazillion-story-high apartment towers sprout up across the city, buildings with character are more in demand than ever. A nice brownstone, of course, is one antidote to the flurry of dime-a-dozen fishbowls. But the answer for New Yorkers seeking a truly unique space is the conversion. In the past few years, both Anderson Cooper and Terry Richardson renovated former firehouses, and one of the priciest penthouses in Brooklyn right now is a converted clock tower. Such spaces are often crammed with unusual amenities (massive timepieces, horse-head-accommodating windows)—and that’s precisely the point. Here, a look at five homes that have undergone mammoth transformations, plus the nitty-gritty specifics of deconsecrating a church, salvaging a fire pole, and finding that elusive convertible in the first place.