Renovation of Hotel Schweizerhof and construction of the Migros Shop was a rather controversial project: demolition of the wing of the old hotel occupied by the stables and the kitchens to build a new shopping centre attracted bitter criticism.
At the competition stage, it was feared that the big hall in the hotel built between 1863 and 1865 by Leonhard Zeugheer would also have to be sacrificed, but the winning project by Diener&Diener managed to find the right compromise between the demands of the town planners and those of the architects.
Diener managed to solve the difficult problem of inserting a new building in an established context featuring a building with a significant impact on the town, based on the form of the nearby Matthäuskirche.
The building's exterior has the classical stereometry of a cathedral: rigid volumes forming three naves, the highest in the centre, in an independent block which stands out from its surroundings.
By aligning the body of the building with the hotel and creating asymmetries with the surrounding buildings, Diener manages to make a rather tight corner feel larger, cutting out fascinating perspectives such as the one facing onto Hertensteinstrasse, where the inclination of the building with respect to the axis of the road makes it stand out even from a distance.
The building's strongly monolithic effect is partly a result of the solidity of its finish of oxidised copper plating forming a grid which marks the floors in the building, within which its few but large windows are placed.
Smoked glass with greenish highlights helps create a sense of continuity between full and empty parts of the building so that it appears to be covered with a single skin, a continuous surface that gives it a marked identity in the town.
The hall of the commercial area in the lower part of the building and the reinforced steel skeleton permitted organisation of internal sales outlets in a free floor plan.
Above the commercial area are the classrooms of the "Migros school": a school promoted by Migros where adult education courses are offered in languages, information technology, decorative arts, cooking and sports.
The classrooms on the second floor are arranged along a glassed-in gallery overlooking the shopping centre, creating visual relationships among the various functions of the building; the classrooms on the upper floor have large windows overlooking the rooftops of the side naves.
The school also includes a gym and music classrooms in another building behind the hotel, also designed by Diener. This building has a less monumental appearance: a glassed-in cube where the stripes marking the floors, plastered white, create a strong sense of horizontality and add motion to the façades.
The result is particularly natural, modern architecture, thanks to the rigour of Diener's design, which uses simple volumes and makes materials and assembly elements the essential theme of the façade, like the copper plates with their clear, precise outlines, clearly distinguishable and recognisable, lending character and personality to the whole building.