We've long been obsessed with Clinton Hill's Broken Angel building. It sits on the corner of Downing and Quincy, just a few blocks South of Pratt, but it's visible from a bunch of spots around the neighborhood. The building is a work-in-progress by Arthur Wood, a "self-taught" architect and painter. It resembles a Brooklyn tenement version of a Antoni Gaudi building-- compare the exterior to the Sagrada Famiia church, or Casa Battlo in Barcelona. According to this Times article from 2002, Wood bought the building in 1971 for $2000, and has been working on it ever since.
If you've never seen Broken Angel, you're in luck. Corie sent in this link to a 111-picture Broken Angel set on Flickr. JimmyLegs says the pix were taken by Arthur Wood's son! The set is full of amazing interior shots complete with dusty dolls, strange stained glass, and half-completed walls. There are also cat-shots! Check them out.