Hole in bedrock; dumped filling used in leveling.
Probably a natural water line, tending to wash out, has been cut back for various purposes, and finally all filled in to make level bedding for 4th c., ... Ca. 350-270 B.C.
Tzochev, Chavdar ... The American School of Classical Studies at Athens ... The Athenian Agora: Results of Excavations Conducted by the American School of Classical Studies at Athens 37 978-0-87661-237-8 ... 2016