At an elevation of -213.5–214.1 m below sea level (map ref. NIG 2603/7485; OIG 2103/2485) the foundation remains (0.4–0.5 m wide) of a building (2.5 × 2.5 m) whose exterior face consisted of large ashlar stones (0.30–0.35 × 0.35–0.40 × 0.45–0.55 m) and rubble bonded with mortar were exposed (Figs. 1, 2). Remains of carbonized wood and grain seeds found in the mortar were dated by Carbon 14 analysis. A sample (RT 4447) that was cleaned to remove the inorganic remains and humic acids was dated to 1480 ± 40 BP (a calibrated date of 530–660 CE).

The function of the building is unclear; the foundations could have been used as the base of an observation or guard tower. An analysis of the plaster revealed that it consisted of burnt lime and ash mixed with small basalt temper and crystallized and hardened in dry conditions on land. Since this kind of plaster cannot harden underwater it is apparent that when the building was erected (sixth–seventh centuries CE) the level of the Sea of Galilee dropped to an elevation below -214 m. When the wind blows from the west, the eastern shore of the Sea of Galilee is stormy and the waves can reach a height in excess of 1.5 m. Thus, it is reasonable to assume that when the building was constructed the level of the lake was at least one meter lower than the building’s foundations. Hence, we can conclude that at some time in the sixth–seventh centuries CE the level of the Sea of Galilee dropped to an elevation of -215 m or more, probably as a result of several years of drought. This is the lowest known level of the lake in historic periods