Referring to the site of B:HUB, an imposing 980-foot-long by 140-foot-high office complex skirting the S-Bahn in Berlin’s Friedrichshain district, architect Frank Barkow says, “We call this an infrastructural infill condition. It’s a site typology that keeps coming up in our work.” Similar overlooked properties scattered along this surface-rail system intrigue Barkow and partner Regine Leibinger for their development potential, particularly as local real-estate values rise, and they become more attractive for large-scale interventions that could enrich urban life (an interest the duo explored in design studios they conducted at Princeton University from 2016 to 2019.)