The indoor installation was completed on April 6, 1999 in the Gasometer Oberhausen and remained until mid-October 1999.

The Gasometer, one of the largest gas tanks in the world, 384 feet (117 meters) high by 223 feet (68 meters) in diameter, was built in 1928/29 to store the blast furnace gas (a by-product of the industrial processing of iron ore). Christo and Jeanne-Claude were invited by IBA Emscher Park Organization (founded by the state of North Rhine-Westphalia in 1989 to improve the infrastructure of the Ruhrregion), to exhibit in the Gasometer in Oberhausen.

The 13,000 oil barrels wall was 85 feet (26 meters) tall and 223 feet (68 meters) wide with a depth of 23.7 feet (7.23 meters), and spanned the distance from wall to wall of the Gasometer. The barrels (208 liter capacity each) were connected to a structural core made of steel scaffolding structure to which they were bolted. The entire wall of barrels was supported by steel pillars resting on the foundation of the Gasometer, and not connected to the steel structure of the Gasometer.

The barrels had been specially painted in bright industrial yellow, deep orange, ultramarine blue, sky blue, rock gray, light ivory, and grass green. The barrels were stacked following a predetermined pattern. 45% of the barrels were yellow, 30% deep orange, and between 2% and 6.6% for the other colors. The total weight of the wall was 300 tons. After the exhibition, The Wall was removed and all materials went back to their usual industrial uses.

The artists' friend and exclusive photographer, Wolfgang Volz, was the project director in charge of the planning and construction of The Wall.

Within the dark enclosure of the gas container the multicolored mosaic of the 13,000 oil barrels wall stood out with luminosity.