The film is also concerned with a number of other themes, including: time, poetry, technology, home, war, politics, myth, National Socialism, the Holocaust, the ancient Greek polis, Sophocles, Antigone, Agnes Bernauer, Edmund Husserl, the 1991 battle of Vukovar, and the 1999 NATO bombing of Yugoslavia.

The Ister features extensive interviews with the French philosophers Bernard Stiegler, Jean-Luc Nancy, and Philippe Lacoue-Labarthe, as well as with the German film director Hans-Jürgen Syberberg.

Other interviews are conducted with a bridge engineer (Nemanja Calic), an amateur botanist (Tobias Maier), and a Romanian archaeologist (Alexandru Suceveanu).

The film travels upriver: from the Danube Delta, opening onto the Black Sea in Romania, to the source of the river in the Black Forest of southern Germany, moving along the way through the Histria (Sinoe) archaeological site, through Novi Sad in Serbia, Vukovar in Croatia, Budapest, Dunaföldvár, and Dunaújváros in Hungary, and Vienna and the Mauthausen-Gusen concentration camp in Austria.

Also featured are the Walhalla temple near Regensburg, the Befreiungshalle at Kelheim, the tomb of Agnes Bernauer, and the castle at Sigmaringen to which Marshal Pétain fled in 1945. Notable places from Heidegger's own life which feature in the film include his birthplace in Meßkirch, his hut at Todtnauberg, and the lecture theatre at Freiburg University where he delivered his infamous Rectoratsrede (rectorial address).