The Pneumatit AG had created a small, publicly accessible concrete garden in Rheinau. In duplicate, there were side by side for testing: one concreted path, a small square with a stele and a sitting sphere on it – once with, once without Pneumatit®. A short introduction was attached to a third stele. The solution (“Which is with, which is without Pneumatit®?”) was visible concealed on the opposite side of the street. – The test facility had to be removed for maintenance reasons.