Liquid nitrogen tanks on the street

In New York City, particularly in midtown Manhattan, one often sees big metal tanks of liquid nitrogen on the street._ I presume these have something to do with what’s going on under the street, as there are usually tubes going from the tanks to holes in the ground.

What are these for?

Sometimes cables are pressurized with nitrogen gas to keep out moisture. After splicing, such cables must be purged and repressurized, and that’s what these tanks are for.

Ha! I wondered the same thing. See Liquid nitrogen canisters on sidewalk for the answers I got to the question.