We are big fans of River House, the stately old East Side co-op that's so prestigious, brokers are told not to mention the building by name (though some would argue the building is a has-been). Specifically we love the rooms of River House, because old-money style doesn't get any older, friends. So it's with great pleasure that we point you to the newest listing in the building, #15B, a 3BR/4.5BA slice of floorplan porn (lovin' that terrace!) asking $8.25 million. Showings don't begin until next week, but here's a preview. Musty!