Located beneath line of Poros Gutter, from a square settling basin cut in bedrock at the north end of Trench II, South of Theseion, 1.30m below the modern road surface. The basin is lined with rough-picked ... Last quarter of 5th c. B.C.-early 4th c. B.C ... Located beneath line of Poros Gutter, from a square settling basin cut in bedrock at the north end of Trench II, South of Theseion, 1.30m below the modern road surface.