Built during the last years of the 19th century, the four buildings were a curious and imposing feature of the city’s landscape ( 72 m in height with an inside diameter of 61 m) with their arcade windows and a wealth of construction details. The renovation has preserved the spirit of the place. In fact, this historical witness to an industrial architecture unique in its kind in Europe has been kept intact by the architects. After dismantling the four iron reservoirs and preserving the outside facade, they created new, transparent volumes, bathed in natural light.

The work of Jean Nouvel, tower 1 includes 9 structures of 14 levels, encircling the inside space. These reconstructed spaces are slightly detached from the original wall in such a way as to release vertical accesses. For tower B, Coop Himmelb(l)au created a closed circular volume looking over an inside patio, adding a building of 18 floors. Tower C by Manfred Wehdorn has a similar structure, opening out onto a landscaped patio and in tower D, designed by Wilhelm Holzbauer, the central building in the form of a three branched star creates three small courtyards opening up towards the walls of the former facade.