Settling basin

Well-known drawing of J.B. Piranesi of a settling basin (in a branch) of the Aqua Virgo although Frontinus
notes that the Virgo - in his time - had no settling basins at all (Frontinus 22) so this one must
be an addition of later date. The Virgo water enters at A, drops via B and C into chamber D and
also fills F via opening E. In the lower chambers the water calms down, leaving impurities
behind that periodically had to be removed via K. The water leaves the basin at I via opening
G and chamber H.