Altar of the Twelve Gods (Athens - Piraeus metropolitan area)

This altar ("bômos" in Greek) in the center of the agora was dedicated to the twelve great gods of Greece : Zeus, Hera, Poseidon, Demeter, Hestia, Apollo, Artemis, Hephæstus, Athena, Ares, Aphrodite and Hermes. It was the point from which distances were reckoned.
www.agathe.gr/cgi-bin/qtvr?site=agora(360 virtual tour)
plato-dialogues.org/tools/agora.htm