Monolith

I did not take this picture, but just wanted to share the monolith that first appeared here in Utah, 200 or 300 miles from me.  It was taken away from this location, although no one seems to know by whom.  Since then, monoliths have appeared in several different locations, including Alaska, Pennsylvania, Colorado, England.....  Reminds me of 2001: A Space Odyssey.  Any ideas what they are and where they came from?