The firebox included a curved wall, a round surface and an opening. The wall (W10; inner diam. 3.17 m, outer diam. 5.10 m, height 1.5 m), preserved seven courses high, was built of large ashlar stones (0.24 × 0.44 × 0.60 m) that were lined on both sides with different size fieldstones, bonded with soil. Traces of soot from the fire were evident on the stones. The round surface (L304; diam. 1.65 m, preserved height 1.1 m; Fig. 2) was exposed in the center of the area enclosed by W10. The surface was built of small ashlar stones, set upon bedrock, which bore clear identifiable signs of ash and burning. The opening, set in the eastern side of the installation (L307; width 1.8 m, height 1.82 m), was built of ashlar stones (0.2 × 0.3 × 0.5 m). The vault was enclosed between two walls, aligned north–south (W11, W12), which were adjacent to W10 and continued beyond the limits of the excavation area. Walls 11 and 12, preserved two courses high were built of ashlar stones. The floor of the vault (L309) consisted of tamped brown soil and small stones. The vault was blocked with collapse of stones and soil (L308).
Fragments of pottery vessels were discovered on the floor of the installation, in the fill within the opening and between the stones of W10; these included a bowl (Fig. 3:1), cooking pots (Fig. 3:2–4) and jars (Fig. 3:5–9), dating to the Roman period (first century CE). Fragments of wasters were also found.