Eclipse (STS) + Maven

Is there a way to invoke maven console from eclipse? (where I could write eclipse:eclipse, and it started building eclipse project)

You could open a shell inside eclipse , cd into the right directory and run the maven console from there. But, when using M2Eclipse (see next point), you're not supposed to run eclipse:eclipse.

Where does STS unpack it's maven? I'd like to add that path to env variables, so that I could use it from my windows console.

STS bundles M2Eclipse which comes with an embedded version of Maven (so it doesn't "unpack" Maven). But you can Configure M2Eclipse to use an external version. Go to window > Preference > Maven > Installations and Add... your external install: