It's a bit a lot of things. I can't find when the building was built, but I'm guessing the 60s/70s, so pretty much the height of brutalist architecture. Basically, very hard geometric forms, heavy on repetition, lots of concrete. There's a lot of that type of stuff sitting around, especially on university campuses.

It appears to be have been actually designed for use as a telephone switching center, for which windows actually are mostly useless. Should take a look at http://en.wikipedia.org/wiki/33_Thomas_Street, another telephone exchange in NYC. It is literally a window-less skyscraper.

That's the place. On the corner of 2nd and Folsom.