[en] The website of Swedish publishing house Bonniers presents Tomas Tranströmer as “one of the most genuinely Swedish poets, masterful in his visions of interior and external coldness and barrenness”. An acclaimed master of the short poem, Tranströmer's 1974 Östersjöar (Baltics in the English translation) is his most ambitious attempt to write a long poem. It is also the only one of his books in which he names and thematizes a precise geographical reality. This article offers a reading of Baltics that shows how the geographical space of the Baltic sea participates in the construction of a deeply personal poetical territory of which it becomes an essential part. The form Tranströmer gives to his longest poem is intimately linked to the themes which it develops and makes of Baltics a central book in his poetical output as a whole.