This photo shows an arch form used for tunnel concrete operations on the east tunnel of the Second Avenue Subway. (credit: Metropolitan Transportation Authority)
Second Avenue Subway Construction
Waterproofing of the east tunnel of the Second Avenue Subway. (credit: Metropolitan Transportation Authority)
Second Avenue Subway Construction
Building an entrance to the Second Avenue Subway's 72nd Street Station. (credit: Metropolitan Transportation Authority)
Second Avenue Subway Construction
Mining the cavern that will house the Second Avenue Subway's 72nd Street Station. (credit: Metropolitan Transportation Authority)
Second Avenue Subway Construction
(credit: Spencer Platt/Getty Images)
Second Avenue Subway Construction
(credit: Spencer Platt/Getty Images)
Second Avenue Subway Construction
A Metropolitan Transportation Authority (MTA) worker walks in an underground tunnel for the long-proposed 2nd Avenue subway line on April 12, 2007. (credit: Spencer Platt/Getty Images)
Second Avenue Subway Construction
(credit: Spencer Platt/Getty Images)
Second Avenue Subway Construction
(credit: Spencer Platt/Getty Images)
Second Avenue Subway Construction
(credit: Spencer Platt/Getty Images)
Second Avenue Subway Construction
(credit: Spencer Platt/Getty Images)
Second Avenue Subway Construction
Second Avenue Subway project (credit: Spencer Platt/Getty Images)