The building techniques he uses are based on the ancient Sumerian reed houses of Mesopotamia and the traditional European small outbuildings constructed of woven plants and trees. Yet while both these were built of tightly bound reeds and green branches, Kalberer's structures uses the whole tree which is woven in place to form a living structure.
Sanfte Strukturen built its first public willow structure in 1998, The Auerworld Palace in Auerstedt, Germany.
All woodcutting, binding, planting and construction was done by hand accompanied by lots of music and frivolity. Kalberer described the unconventional building process as somewhere between a chain gang and a party!
Today the Palace is a major tourist attraction in the countryside between Weimar and Naumburg. It is home to full moon dance parties known as the Auerworld Festivals, which is said to draw more than 80,000 visitors.
It is the 'mother of all willow palaces' - the first large scale example of botanic architecture in the world.
Marcel Kalberer prefers the term "living architecture" because of the botanical and ecological implications and because all his structures are created by a community of volunteers.
This is not the rarified world of conventional architecture dominated by professionals and experts - it is more like a community barn raising as we see in the Amish tradition.