Scholars long suggested that Channel II directed water along the eastern border of the City of David to irrigate adjacent agricultural plots and that it ended in a pool at the southern end of the city. But the authors’ excavations reveal that a subsidiary tunnel (Tunnel III) deflected water directly into a deep pool, protected by the Pool Tower. Grooves chiseled into the pool’s walls may have supported a wooden platform from which several people could draw water at the same time.