It’s rush hour in Fulton Center and thousands of black-coated commuters stream into the glass building through entrances on Broadway and Fulton Street and funnel down to the hovering circular concourse before branching off to further descend to the many tunnels that transverse New York’s five boroughs. A steady hum of voices backgrounds the incessant chirp-crank, chirp-crank of the subway turnstiles and the occasional click of digital shutters Instagramming the conical metal dome that dominates New York City’s shiny new transit nexus, which is already being called downtown’s Grand Central Terminal. Building anything so complex — especially infrastructure, especially in lower Manhattan — is an impressive feat, but it takes more than efficient planning and techno-artistry to make a space grand…