When New York’s St. Vincent’s Hospital closed in 2010 after years of financial strife, Greenwich Village lost a beloved 150-year-old institution that had served the poor and working class and was “ground zero” when the AIDS epidemic erupted in the 1980s. While most of the St. Vincent’s campus was demolished, a quirky precast-concrete building on Seventh Avenue between West 12th and 13th streets, designed by Albert Ledner and completed in 1964, remained. St. Vincent’s purchased it in 1973, but Ledner had designed the building to house the National Maritime Union Headquarters—hence its sturdy rectangular form and scalloped rows of porthole-style windows on the fourth and fifth floors.

Fast-forward to July 17, 2014: the O’Toole building, as it was known during its St. Vincent’s tenure, reopened its doors as the Lenox Hill HealthPlex, a stand-alone, 24-7 emergency department that is a division of Lenox Hill Hospital in Manhattan. Once again, Greenwich Village has an emergency health-care resource and a lovable, weird New York building has been preserved, even as waves of new development rise around it. The facility also represents a countrywide trend. “We’re seeing a transformation in health care into this ambulatory environment,” says Jeffrey Brand, planning principal with Perkins Eastman’s national health-care practice, which turned the O’Toole building into the HealthPlex. “We probably have about eight projects that are all like this.”

By “like this,” Brand means outpatient, stand-alone, one-stop shops for emergency care and day surgery, with pharmacies, imaging, labs, and sometimes cancer care all in one building. “Empirical evidence clearly points to the fact that you do better if you go home every night” rather than stay in a hospital bed, “and these are less expensive buildings to put up,” he says. Like the O’Toole building, many older buildings—from bowling alleys to shopping malls—are being converted into these health-care settings because they are in downtowns, often have pre-existing parking lots, and are easy for people to get to. The Affordable Care Act (which means that hospitals are trying to process more patients) and advances in technology that allow for speedier care are aligning to spur this trend. “It’s a brand-new world in health care, and it’s going to be very efficient for institutions and better for the consumer,” says Brand.

For Perkins Eastman’s New York office, painstaking restoration of the building’s exterior and the adaptive reuse of its interior (from “dumb” medical office building to high-tech emergency department) was a prize of a project. The architects worked to bring it back to Ledner’s original vision, even talking to Ledner (now in his 90s) about their plans. “The one thing I found really fascinating was Ledner’s belief in the power of the circle,” says Duncan Reid, the design principal for the project. “He believed that the circle was the most democratic of all forms because there are no corners. We thought, ‘Wow, that’s a powerful message. Let’s continue that, because the doors are open here for all. We wanted to provide the needed health care here in the Village, given what happened with St. Vincent’s.”

The building is not landmarked, so Perkins Eastman had an easier time retrofitting it for its new function, but it is in a historic district, and the client received historic-preservation tax credits, “so we went even further with our oversight. The state historic office reviewed a lot of things,” says Brand. The architects removed tiles that the National Maritime Union had added to the concrete-paneled facade in 1966, and conducted a scientific analysis of the original paint to match its precise shade of white. The building sits on a plinth, part of which St. Vincent’s topped with rocks. Perkins Eastman removed them, and an ugly fence, and reconstructed the original concrete platform with its checkerboard pattern, adding wheelchair ramps. The architects gutted the interiors, inserting a cutting-edge medical facility on the ground floor with state-of-the-art imaging, surgery, and emergency-medicine technology. The upper four floors will eventually house office space for physicians, ambulatory surgery, and imaging.

Those floors always sat on a pedestal of two intersecting circles, looking like a Venn diagram in plan. The pedestal was made of glass blocks, which the architects replaced (some of the exam rooms are on the other side of these beautiful walls, benefiting from soft daylight while still maintaining privacy). They added a new glass entry vestibule; small patient waiting rooms to the north and south of the entry are rarely full, explains Reid, because the HealthPlex is designed to usher patients right into exam rooms for evaluation and treatment.

The open, airy emergency department has two internal “streets” flanking nurses stations encircled by more rooms for exams and medical tests. Perkins Eastman removed a portion of a mezzanine level that was not original to the building to create higher ceilings above the emergency department. Three curved, sail-like ceiling planes above the nurse stations are faced in acoustic panels. The architects pulled out the north wall of the circle to create more rooms for patients. To the south, they removed a shear wall so that ambulances could pull in off the street. The biggest design challenge, says Reid, was trying to “fit in little individual rooms in a circular floor, and stuffing in all the 21st-century requirements of air, water, and medical gasses.” They turned an underground parking garage into a lab, staff lounge, and other services. (Across West 12th Street, an old St. Vincent’s mechanical building will be razed to make way for the New York City AIDS Memorial, designed by Brooklyn’s Studio a+i.)

The HealthPlex is expecting to treat 20,000 to 25,000 patients per year (it could accommodate 45,000 if necessary), according to executive director Alex Hellinger. “We don’t have a 200- to 800-bed hospital above us competing for the lab and CT scan. You could wait a few hours [in that environment],” he says. The HealthPlex is not a trauma center, and when surgery is required—even though its board-certified surgeons have the capability to crack open a chest, says Hellinger—patients are stabilized and then sent to other hospitals. “As the community comes in, they start to realize, getting to a hospital bed is not important: it’s getting to the first point of contact.”