April 4, 2016 8:00 AM EDT

Almost 90 years ago, Manhattan’s 60 Hudson Street was the nerve center for the most vital communications system in the world: the telegram. Today, the medium has changed, but the mission remains the same. The building at 60 Hudson is now the home of the Internet.

Well, part of the Internet. The 24-story art-deco building is what’s known as a “carrier hotel,” a hub where telecommunications companies exchange Internet traffic to boost efficiency. There are five such hotels scattered around New York, according to Wired, housing everything from large Internet Service Providers like AT&T, to consumer tech giants like Google, to tiny startups in need of server space and blazing-fast speeds.

The hotels are closely guarded, as you might expect for such vital infrastructure. Security guards, retina scanners and “mantraps,” which keep possible intruders detained until they are apprehended, are just some of the facilities’ defensive mechanisms.

But photographer Peter Garritano was granted access to five of the New York facilities, gaining an inside look at the physical space that helps carry the digital content we summon every day. The rooms are full of snaking wires, endlessly stacked boxes of servers and massive diesel engines ready to churn to life in case of power failure. The Internet may feel weightless, but it has mass, volume and even temperature—60 Hudson’s roof is lined with fans to help remove heat exhaust.

The Internet’s physical presence will only grow from here. There are already more than 3 million data centers in the United States. With U.S. Internet traffic expected to nearly double by 2019, there are doubt be many more to come.

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