The article presents Juliusz Slowacki's diary from his East voyage (1836-1837) to Grece, Egypt, Palestine, and Lebenon lost for 70 years. The diary was found in the collection of Russian State Library in Moscow. Considered to have been burnt with most of manuscripts of Krasinski Library after the Warsaw Uprising in autumn 1944, it was actually borrowed in 1939 to be displayed at high school in Krzemieniec. It was probably in Krzemieniec that it was confiscated by the Soviet authorities after September 17th, 1939. The diary, written by Slowacki himself, contains a number of popular pieces with A Voyage to the Holy Land from Naples, notes, voyage diary, daily records, and so-far unpublished landscape sketches. Diary notes, poetic works and samples build an interconnected set of the poet's live report while facing the exotic culture of Greece, Egypt, and the Near East. The diary is the basic source of the history of Slowacki's voyage to the East and invites a new research into the poet's artistic process.