Even with a Canal Street location and, um, noticeable design, the Zinc Building's difficulty selling penthouses is something of a puzzler. We thought Penthouse East (now off the market) was the last one left, understandable given its view of Canal and the Holland Tunnel, but it looks like there's one more, Penthouse B. The apartment was originally listed for $7.25 million in 2010, chopped to $6.95 million early this year, and taken off the market in May. It appears not to have sold, because it's back and asking a slimmer $5.95 million. The interiors leave us a little cold, but the 981-square-foot rooftop terrace lets some heat in.