“Well-established” may be too strong wording, but Greek sailors and traders were certainly familiar, and people generally were familiar with Gades and other set

“Well-established” may be too strong wording, but Greek sailors and traders were certainly familiar, and people generally were familiar with Gades and other settlements. I am not sure if there really was a Greek colony as well at the time of Plato in the Portus Menestheus, although the Greeks believed they had founded one there after the Trojan War. There’s also Greek stories and lesser familiarity as well at some point with Tartessos (another possible Atlantis.)