With more than 100,000 square feet of interior and exterior amenities, residents of the Extell-developed One Manhattan Square have no shortage of exciting activities at their fingertips this summer—and beyond. Those who call the building’s Lower East Side condos for sale home can relax on the elegant West 8-designed terrace, which boasts a long list of luxe features, including outdoor grilling and dining space, fire pits, a children’s playground, a putting green, and an adult treehouse where grownups can channel their inner child.