How to get the Maven local repo location?

Yes, you can get it with the -X or --debug option, e.g. mvn -X

...
[DEBUG] Reading global settings from C:\Maven\conf\settings.xml
[DEBUG] Reading user settings from C:\segphault\.m2\settings.xml
[DEBUG] Using local repository at C:\Repo
...

If you want just the local repo, try this:

mvn help:evaluate -Dexpression=settings.localRepository | grep -v '\[INFO\]'

EDIT

I'm revisiting this after years because recent versions of the Maven help plugin introduced a useful parameter for the evaluate goal called forceStdout that allows us to remove the need to grep the output:

mvn help:evaluate -Dexpression=settings.localRepository -q -DforceStdout