This annual festival gives attendees access to more than 150 of the city’s coolest and most exclusive architectural sites, private homes and landmarks, plus behind-the-scenes tours and programs. This year, get a sneak peek of the 72-story 4 World Trade Center before it opens to the public, see the inner workings of the Sims Sunset Park Recycling Facility—designed by cutting-edge firm Selldorf Architects—and tour the exterior of the new Whitney Museum building alongside the High Line. You’ll also have another chance to see many places you might have missed last year, including the ornate Grand Lodge of Masons, the dramatic Newtown Creek Wastewater Treatment Plant with its giant stainless-steel digester “eggs,” Philip Johnson’s masterful modernist interiors for the Four Seasons, and Eero Saarinen’s TWA Flight Center at JFK. Look for the full schedule (and the ability to preregister for certain events) in the first week of October.

Newtown Creek Wastewater Treatment Plant Photograph: Donald Yip