63 Greene Street is one of the few remaining SoHo buildings to be converted for residential use. Three penthouse lofts are available for purchase on the sixth floor. Vaulted brick ceilings with exposed beams and steel-clad columns define the cast iron era architecture. This district of SoHo comprises about 500 buildings, characterized by their cast-iron facades which was first developed in the 18th century. Cast-iron buildings. The use of cast-iron construction allowed for ornate facades that were a more cost-effective alternative to granite and marble.