The Symplegades were a pair of rocks at the Bosphorus that clashed together randomly. Jason and the Argonauts were able to slip through them by following the advice given to them by king Phineas.

Cyanean Rocks

Clashing Symplegades
Threatened the Argo with
One crushing wreck;
Thanks to Athena, the
Plan was successful, no
Damage to deck.

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