The view inside a cistern. The cap on this household cistern, part of an interconnected series of cisterns at Ai, was set in place during Iron Age I (1200–1000 B.C.E.) and remained undisturbed until excavations in the 1960s. Cisterns cut into bedrock such as this are typically bell-shaped (see drawing). The development of iron tools to dig such pits and the introduction of terraced farming are two technological innovations that facilitated the settlement of the proto-Israelites in the central hill country of Canaan.