The medical practice of Columbia University's College of Physicians and Surgeons, College of Dental Medicine and School of Nursing has moved to a much bigger location that will also give it easy access to thousands of workers in midtown offices. ColumbiaDoctors Midtown opened earlier this month at 51 W. 51st St., between Fifth and Sixth avenues and across from Rockefeller Center after years at 16 E. 60th St. It is ColumbiaDoctors' largest off-campus ambulatory care multispecialty office. With its 15-year lease on East 60th coming to an end, ColumbiaDoctors found a 125,000-square-foot space on a single floor that it could build out to its specifications. The setting accommodates 125 exam rooms and 20% more patients. The average cost of construction of health care practices, including equipment, is roughly $400 a square foot. The new site has a somewhat rare 25-year lease. Many hospitals have expanded their geographic reach by acquiring practices or opening sites in their competitors' backyards. ColumbiaDoctors has about 17 sites now, with growth fueled by recruiting new faculty. The 200 people added last year all need space to practice, and ColumbiaDoctors has expanded into far-flung locations in Westchester, Rockland and Orange counties. Clinical revenue is up by more than 5% in each of the last two years. Fueling the expansion is the trend of "more care being delivered in the office and not the hospital," said Dr. Lee Goldman, executive vice president and dean of Columbia University Medical Center. "As a result, ambulatory care facilities are growing." Columbia's competitors, most notably the ambulatory care practices of Mount Sinai Hospital, Continuum Health Partners and NYU Langone Medical Center, also are rapidly expanding. "We're not expanding because we are competing," Dr. Goldman said. "If other people are expanding as well, that's OK. The demand is there." The midtown practice, which has some 225 physicians, dentists and nurse practitioners, already accommodates 700 patients daily, but it can handle about double that volume. The clinic offers cardiology, executive health, pre- and post-surgical care, psychiatry, radiology, travel medicine, women's health and laboratory services. While the previous site was in more of a residential area, the new one is in the business heart of Manhattan, allowing patients to squeeze in appointments during the workday. Services are available early morning and evening hours and on Saturdays. The practice is working to have more departments open during off hours. ColumbiaDoctors plans to market its services to 40 to 50 large employers in the neighborhood, said Mark McDougle, CUMC's senior vice president and chief operating officer. "We're sketching out a schedule to start meeting with them," he said.