and the one looking west says,

"This is Peloponnesus, not Ionia."

And also he instituted games there, in emulation of Herakles; that, just
as Herakles had ordained that the Greeks should celebrate the Olympic
games in honour of Zeus, so by Theseus's appointment they should
celebrate the Isthmian games in honour of Poseidon.

The festival which was previously established there in honour of
Melikerta used to be celebrated by night, and to be more like a
religious mystery than a great spectacle and gathering. Some writers
assert that the Isthmian games were established in honour of Skeiron,
and that Theseus wished to make them an atonement for the murder of his
kinsman; for Skeiron was the son of Kanethus and of Henioche the
daughter of Pittheus. Others say that this festival was established in
honour of Sinis, not of Skeiron. Be this as it may, Theseus established
it, and stipulated with the Corinthians that visitors from Athens who
came to the games should have a seat of honour in as large a space as
could be covered by a sail of the public ship which carried them, when
stretched out on the ground. This we are told by Hellanikus and Andron
of Halikarnassus.

XXVI. Besides this, according to Philochorus and other writers, he
sailed with Herakles to the Euxine, took part in the campaign against
the Amazons, and received Antiope as the reward for his valour; but most
historians, among whom are Pherekydes, Hellanikus, and Herodorus, say
that Theseus made an expedition of his own later than that of Herakles,
and that he took the Amazon captive, which is a more reasonable story.