“Vancouverist” architect Bing Thom gave Washington a new architectural gem with his design for Arena Stage’s Mead Center for American Theater in 2010. Next he’s doubling down in D.C.’s Southwest neighborhood, with a new museum and hotel for art collectors Don and Mera Rubell (who own the nearby Morris Lapidus–designed Capitol Skyline Hotel). Thom, whose work is synonymous with walkable neighborhoods and transparent buildings, thinks much of blocky, modern, concrete Southwest can be preserved and adapted. The National Capital Planning Commission and other stakeholders would like to speed that adaptation up in a neighborhood transformed by 1960s Modernist experiments and subsequent decades-long economic blight. Some say Southwest’s problems start with architects such as I.M. Pei, but the NCPC isn’t blinking over this new architecturally driven plan, which would turn part of the neighborhood into a High Line-esque “Ecodistrict” replete with buzzy green features. That, plus a major development for the Waterfront, could turn around fortunes over on the wrong side of the National Mall. The biggest changes coming to Southwest may yet be in the offing: The U.S. General Services Administration, under acting director Dan Tangherlini, has posted notice that it will consider redevelopment plans for Federal Triangle South, a cluster of five, block-busting federal buildings that cuts off Southwest from the rest of the city.