Even today, the author and the date of the “Situs orbis descriptio” or “De situ orbis”, also known as “Orbis descriptio”, a didactic poem in Greek of 1187 hexameters, which served as a poetic guide to the world known in antiquity (periêgêsis tês oikoumenês), seem to be an enigma. Much ink has been spilled on the question of the age and country of Dionysius, until G. Leue (Philologus 42 (1884), p. 175 ff.) had the perspicacity to note that the poem is signed and dated; Lines 113-134 (Müller) and 522-532 are acrostics, informing us respectively that the work is “Dionusiou tôn entos pharou”, by “Dionysios, one of those of Pharos”, that is, of Alexandria, and “epi Hadrianou”, “of the time of Hadrian”. (HJ Rose, “A handbook of Greek literature”, London 1965). The poem opens with an introduction (1-26), then the Ocean is treated (27-169), followed by Africa (170-269), Europe (270-446), the islands (447-619) and Asia (620-1165). Callimachean's pleasant and clear versification and its comprehensibility make it an ideal book of the Byzantine school.