Claes Oldenburg installed three giant billiard balls in a lakeside park in Munster in 1977. Made of concrete, they are 3.5 meters (11.5 feet) in diameter. It was the first work he did together with his wife, the art historian Coosje van Bruggen. The idea was to bring art directly to people, bypassing museums.

At Documenta 7 in Kassel, Oldenburg rammed a huge pickaxe into the ground on the banks of the Fulda River. Oldenburg came up with the motif because the pickaxe was used throughout the city after the Second World War to remove the rubble and rebuild the city, which had been left in ruins.

An artificial water spigot nearly 11 meters high, encircled by the larger-than-life red garden hose connected to it, is located in Freiburg im Breisgau. Here, too, the husband-wife artist couple of Oldenburg and van Bruggen explored the site before selecting an appropriate object for the sculpture. As allotment gardens had previously been located in the park, the pair chose a garden hose.

In the middle of Frankfurt's banking district stands the almost 12-meter-high sculpture made of fiberglass. It shows a tie and collar, representing the business apparel of the city's bankers and hedge fund managers, turned on its head. In this way, the artwork almost appears to be a harbinger of the 2007 financial crisis.

Oldenburg set up an 11-meter-tall bundle covered in knotted rope in Berlin. The bundle, woven through with oversized furnishings, symbolizes the belongings of Bohemian immigrants who had fled in the early 18th century because of their faith. They landed in Berlin and built the Bohemian Bethlehem Church. The sculpture stands on the site of the former church, which was demolished in 1963.

An overturned ice cream cone on the roof of a shopping arcade is one of Oldenburg's favorite works of art. It is inspired by the two towers of Cologne Cathedral, which shape the cityscape. When asked whether the sculpture could be understood as a heavenly sign, he told the local newspaper, the "Kölner Stadtanzeiger" in an interview: "Yes, it is like ice falling from the sky and landing there."

A 1964 silkscreen portrait of Marilyn Monroe, known as "Shot Sage Blue Marilyn," will be auctioned in May by auction house Christie's. The work could sell for $200 million (€182 million), making it the most-expensive 20th-century artwork to be auctioned. Celebrating her iconic status, Andy Warhol made many Monroe works, including five different versions of this portrait, each in different shades.

This self portrait is reminiscent of religious iconography. Andy Warhol's parents came from a village in the Carpathian Mountains (now Slovakia)#, and emigrated to the US in the 1920s via Bremen. His mother was a devout Catholic, and during the hours spent attending mass with her as a child, he would stare for hours at the paintings of Christ and the saints in the church.

After studying commercial art, Warhol initially worked as an advertiser and designer for a shoe manufacturer. He was an early adopter of silk screen prints, and exhibited his early works at the Bodley Gallery in New York in 1959. While promoting himself as an "anti-artist," he also developed a fascination for repetition in his motifs: shoes, cans, eyes — or the lips of Marilyn Monroe.

At the beginning of the 1960s, the young commercial artist started making works of everyday objects, inspired by an art dealer who told him to paint whatever meant the most to him. From then on he created stencils of dollar bills, soup cans, telephones or typewriters. Warhol called this a "reproduction of the everyday." Before him, no one had dared call reproductions of such mundane objects art.

Elvis Presley as a cowboy, Elizabeth Taylor or Marilyn Monroe as a pin-up: Icons of US pop culture were another of Warhol's favorite motifs. These works quickly made him famous in the art scene. In 1962, he exhibited for the first time one of his "Campbell's Soup Cans" paintings: a milestone in art history, establishing Warhol's reputation as the most-renowned pop artist in the United States.

Many paintings and graphic prints by the world-famous pop artist are iconographic. Andy Warhol's painting "Mao," a portrait of Chinese Communist leader Mao Zedong, is available in several color variations as part of a series created in 1972 in Warhol's famous New York City studio, The Factory.

Serial repetition with variations in color became Warhol's trademark. In the mid-1960s, while Warhol also produced music and underground films, he let other members of The Factory create his silkscreen series for him as part of his artistic community.

Andy Warhol often used Polaroids as a template for his serialized paintings; he liked the fact that they captured random moments. He wasn't a fan of elaborately staged works by other contemporary artists of his time. Debbie Harry, front singer of the band Blondie, was immortalized this way by Warhol in 1980. She was also his first guest on the MTV show "Andy Warhol's Fifteen Minutes."

Andy Warhol, who had more than 100 wigs and never left the house without a white-blonde headdress, carried a camera everywhere he went. His photo book "America" was a smash hit in 1985. He dedicated his last painting to the sacrament of Jesus Christ. He died unexpectedly in 1987 following gallbladder surgery.