There’s plenty of tunneling going on underneath the streets of Manhattan. On the west side, digging through the city’s bedrock has given way to interior station fit-ups for the Dattner-designed 7 line subway stations connecting Times Square to Hudson Yards as early as 2014. To the east, sandhogs continue to carve through solid rock for the $4.5 billion Second Avenue Subway Line while other crews outfit the tunnels with concrete and rebar.

Between the two, more massive caverns are being opened up beneath Grand Central Terminal, which turned 100 this month, that will extend the Long Island Railroad to the famed station from Sunnyside, Queens in 2019. The $8.24 billion East Side Access Project will allow commuters to bypass Penn Station and enter Manhattan 12-stories below Grand Central. Now, the MTA has released a dramatic set of photos from inside the 3.5-mile-long tunnel, revealing enormous cathedral-like spaces connected by perfectly cylindrical tunnels. Take a look.

Click on a thumbnail to launch the slideshow. All images courtesy Metropolitan Transportation Authority / Patrick Cashin. [Via Gothamist.]