Tracing invisible hearths and daily routines through carbonised plant remains and geochemical signals in an Early Iron Age smithy at Pungrt Hillfort, Slovenia

• Archaeologically invisible forge hearths may have been portable and raised. • Charred archaeobotanical remains as a proxy for archaeologically invisible hearths. • Archaeobotanical and geochemical spatial reconstruction of activity areas. • Evidence of flatbread preparation during the Early Iron Age in Slovenia. • Evidence of a household-based smithy during the Early Iron Age at Pungrt Hillfort. This study addresses the challenge of locating forge hearths, which are often archaeologically invisible. Specifically, we examine this issue in the Early Iron Age smithy (Building 24) at Pungrt Hillfort (central Slovenia). To tackle this problem, we analysed charred archaeobotanical remains and sediment samples from the smithy’s floor. Our findings indicate that magnetic susceptibility measurements are insufficient for identifying the hearth’s location in contexts characterised by magnetic debris and above-ground fire installations. Instead, the distribution of charred archaeobotanical remains provides the most reliable evidence. In Building 24, these remains successfully revealed the locations of both the forge and charcoal storage. When combined with geochemical data, they also provided insights into the structured use of space within the building. The results further suggest that the low archaeological visibility of forge hearths may be due to their elevation above ground level. Additionally, this study demonstrates that charred archaeobotanical remains are primarily linked to combustion and hearth-cleaning activities, which may skew interpretations of plant use in past societies. However, with systematic sampling of primary contexts, aspects of daily plant-related activities can be discerned. In Building 24, these included hazelnut roasting, potential legume roasting, and cereal dehusking—standard domestic practices suggesting that the blacksmith’s workshop was situated within a domestic building. The evidence indicating flatbread baking is of particular significance, marking one of the earliest documented examples of this type of bread preparation in Early Iron Age Slovenia. This discovery underscores that the smithing hearth was not exclusively used for specialised metalworking but also supported household food production.