8 daring art highlights from 60 years of Documenta

The Documenta has always like to provoke and irritate. French artist Pierre Hughes turned his Spanish greyhound "Human" into a living work of art for Documenta 13 in 2012. Kassel is full of parks, so Human had plenty of opportunity to run around.

At that time, dissident artist Ai Weiwei was still permitted to leave China. At the 2007 Documenta he organized a costly performance work titled "Fairytale," which brought 1,001 Chinese citizens to Kassel. Many of them traveled outside of China for the first time and were able to engage in cultural dialogue at the exhibition.

"Man Walking to the Sky" was shown by Jonathan Borowsky at Documenta 9. It was risky to place such a fragile work outdoors, but it became a symbol of the 1992 show. It was purchased by sponsors and can still be seen in Kassel.

In 1982, for Documenta 7, German artist Joseph Beuys planted 7,000 oaks throughout Kassel. Each was accompanied by one of these basalt Posts.

Documenta practically takes over Kassel when it's in town, including the many green areas in the city. The art collective Haus-Rucker-Co. installed this picture frame in 1977, turning Kassel itself into a work of art - and providing a convenient photo op for art fans.

In 1977, American artist Walter de Maria caused a stir with his "Vertical Earth Kilometer." He drilled a one-kilometer hole into the ground and ran a brass rod all the way down in a symbolic piece marked by absence. After all, the long hole could not be seen.

Pop Art was all the rage when Documenta was just getting started, and the forerunners were in the United States. Andy Warhol's "Marilyn," pictured here much later, was shown in 1968. The work would become one of the most iconic in Pop Art history.

At the very first Documenta in 1955 - just a decade after World War II - director Arnold Bode explains Henry Moore's "King and Queen" to German president Theodor Heuss.