Where is the Library stored?

[rsdio]

I would like to make a backup of my Play.app Library. Where is it stored?
Also, is there anything special I would need to do if I lose my current Library and wish to restore from such a backup?
I recently went back to using Play.app and forgot how the UI worked, so I mistakenly deleted a bunch of files which had no Title, Artist, Album, or Track information. I managed to get everything back by searching my disk and manually adding the files that I wanted, but it would have been nicer if I had a backup because that would have been much faster.

[RonaldPR]

~/Library/Application Support/Play/Library.sqlite3