Description:
"Joseph Beuys never lived in Kassel, but his name is inseparably tied to the city. No other work of art is so thoroughly and lastingly integrated into the topographic and social structure of the city. The planting of a tree alongside a basalt stone in 7,000 points of Kassel began in 1982, as a contribution to Documenta 7, and was finished in 1987, for Documenta 8 [after Beuys's death]."
(actually I'm not sure where this photo was taken)
Beuys lives on in recent "documenta":
http://www.pop.ac/kassel_documenta_10_1997_the_chewing_gum_of_joseph_beuys.html