The Lenbachhaus Museum, which houses some of the most important pieces of art in Germany, is to be revamped for the first time since 1955.
Foster will reorganise and restore the gallery spaces, and the 'antiquated services and technical installations' will be replaced with state-of-the-art systems.
The work aims to maintain the unique character of the garden-fronting facades, while a further building will be transformed into an exhibition space 'fit for the 21st century'.
The building's attic will also be renovated to produce an extra space for exhibitions.
The problem of accessibility has been one of the major reasons behind the work, resulting in a new foyer being designed, which will act as a new visitor hub.
A new entrance will also be built to allow direct access to the café and conference centre independently of the gallery spaces, producing - Foster hopes - a cultural centre as well as a new amenity for the city.