This huge monument of Stonehengian ambitions was erected in 1980 [the year I was born] in Elbert, a rural county of Georgia, US. Work was done by the local granite business, but nobody knows exactly who commissioned the work. Aside from astronomical qualities, The Georgia Guidestones are famous for the controversial tenents engraved in 8 languages on its plates:
I. Maintain humanity under 500,000,000 in perpetual balance with nature.
II. Guide reproduction wisely - improving fitness and diversity.
III. Unite humanity with a living new language.<
IV. Rule passion - faith - tradition - and all things with tempered reason.
V. Protect people and nations with fair laws and just courts.
VI. Let all nations rule internally resolving external disputes in a world court.
VII. Avoid petty laws and useless officials.
VIII. Balance personal rights with social duties.
IX. Prize truth - beauty - love - seeking harmony with the infinite.
X. Be not a cancer on the earth - Leave room for nature - Leave room for nature.
In the last three decades, it goes rising and falling in people's interest, attracting both wonder and hatred. These are interpreted as directions for rebuilding civilization after the apocalypse by some, as the Ten Commandments of the Devil by others, and of course it was already linked with the 2012 fever, occultism, NWO and UFO conspirations. Since 2008, it's a target for many kinds of vandalism...
If you got the time, read the great Wired article on this issue.