Image Credit Maz Hewitt
Gasometers are giant storage tanks that were used to store and balance pressure for town gas (gasified coal) or natural gas. Some were simple and industrial looking; others were elaborate structures. In Vienna they were originally designed in 1896 after a competition, and became such a major part of the skyline that that another competition was held to renovate them, which was one by some of Europe's best known architects, including Jean Nouvel and Coop Himmelb(l)au.
According to Low Waste Building Technologies and Practices:
Four architects won the competition in 1995, Jean Nouvel, Coop Himmelb(l)au, Manfred Wehdorn and Wilhelm Holzbauer, with a different interpretation of each gasometer. Jean Nouvel has created a large indoor plaza with a translucent roof playing with reflections, refractions and transparencies of the old and the new. Coop Himmelb(l)au added a new 22 storeys building to the existing one. Manfred Wehdorn created an indoor garden and an eco-friendly designed terraced structure. Wilhelm Holzbauer occupied the center of the existing building with lift and stairs, from which three compact sections were divided by indoor gardens penetrating the perimeter of the existing building.
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The concept of mixed-use building creates a 24 hours occupancy and activity in the gasometers with inhabitants working, living, and entertaining.