Holderlin's stay in Bordeaux in 1802 still remains a mystery. The only valuable testimony is his famous poem Andenken. On the same page, he started to write a second poem: Der Ister. When Martin Heidegger dedicated two lectures on Andenken and Der Ister in 1941/42, he separated what belongs together. The aim of the study consists in a critic of Heidegger's reading of both poems.