The well-cistern of the Iberian Fortress of Vilars (Catalonia, Spain) is a monumental feature 29 dating to the late 5 th century BCE (Vilars III-IV phases). Management of water resources is key 30 to interpreting the nature of the Fortress as water was essential not only for human and 31 livestock consumption, but for irrigation, construction and crafts. Moreover, water was integral 32 to the site in both times of peace and war as the structures that guaranteed its provision and 33 management coincide with facets of military architecture (moat). Yet why was the well-cistern 34 backfilled with animal remains and other archaeological material only a few years after its 35 construction? To answer this and other questions, this study follows two main lines of research. 36 Firstly, analyses were carried out on the archaeozoological remains collected inside the feature 37 so as to characterise and interpret its nature. Secondly, taphonomic analyses (macro-and 38 microscopic) were undertaken so as to reconstruct the dynamics of the different accumulations 39 and the premature abandonment of the well-cistern's primary function: supply potable water. 40 41 Keywords 42 43 Iron Age, Iberian Peninsula, taphonomy, archaeozoological remains, fortress, well-cistern, bone 44 colorations, chemical analyses. 45 46 47 48