This article argues that Vitruvius’ description of Julius Caesar's ‘discovery’ of the larch (larix, De arch. 2.9.15–16), previously read as a journalistic account of the author's first-hand experience in Caesar's military entourage, should instead be interpreted as a highly crafted morality tale illustrating human progress thwarted. In the passage, the use of larch wood to construct a defensive tower renders the Alpine fortress at Larignum impregnable to assault by fire; only the fear aroused by siege provokes the inhabitants to surrender (...) to Caesar and his troops (2.9.15–16). Nevertheless, the outcome of this discovery is not a complete victory, because the logistics of importing this remarkable timber to Rome are as yet insurmountable (2.9.16). Once the siege of Larignum is recognized as a diptych to Vitruvius’ narrative of the origins of civilization, in which fire and wood likewise play essential roles (2.1.1–7), and compared with similar aitia and source histories across the De architectura, it becomes clear that Larignum and its resources emblematize obstacles to a Vitruvian conception of imperial success, in which the city of Rome catalogues and indexes architectural knowledge amassed throughout the empire. (shrink)