Tuesday a procession of ambulances moved patients out of the University Medical Center of Princeton to a brand new $522 million facility in Plainsboro. The new hospital, the University Medical Center of Princeton at Plainsboro, opened today after a decade of planning and construction. The Plainsboro hospital, at 630,000 square feet, is 50 percent bigger than the old one a few miles away in Princeton. All of the new 231 patient rooms are single-occupancy. Roughly 1,200 studies were consulted to maximize the therapeutic effects of nearly everything in the building, according to Barry Rabner, the president and CEO of Princeton HealthCare System.