The Ister is a 3000km journey to the heart of Europe, from the mouth of the Danube river on the Black Sea, to its source in the German Black Forest. Hailed by Scott Foundas of Variety as "a philosophical feast—at which it is possible to gorge oneself yet leave feeling elated,” the film is based on the work of one of the most influential and controversial philosophers of the 20th century, Martin Heidegger, who in 1933 swore allegiance to the National Socialists.