New York City’s extensive transit system had not been expanded for several decades until construction of the MTA’s Second Avenue Subway program was re-started in 2007. Under Phase 1, the 72nd Street Station and Tunnels Project represents a significant portion of the extensive program. This paper describes the overall project design and unique construction challenges encountered to date for the fast-track excavation and final concrete lining of the underground works. This includes a large span station cavern, cross-over and turn-out caverns, running tunnels as well as three entrances and two ancillary shafts. All work is being performed in a densely developed urban environment, with a restricted surface work site, significant operational constraints and an aggressive construction schedule.