Servian Wall
The observer is standing on the Via Ostiensis at the foot of the Aventine, which is at his back. The river flows toward him. The stone bridge in evidence is the Pons Aemilius. The Servian Wall goes along the bank of the river, is pierced by the Porta Trigemina (you can see the three openings) and starts up the Aventine. Beyond the gate is the Forum Boarium. In the immediate foreground are the docks, or Navalia.