Where are the clashing rocks?

the Bosporusan islet on the European side and a shallow reef on the Asian side of the Bosporus dividing Istanbul.

Where were the Clashing Rocks in Jason and the Argonauts?

the Bosphorus

The Symplegades or Clashing Rocks, also known as the Cyanean Rocks, were, according to Greek mythology, a pair of rocks at the Bosphorus that clashed together whenever a vessel went through. They were defeated by Jason and the Argonauts, who would have been lost and killed by the rocks except for Phineus’ advice.

Where was Colchis located?

Georgia

Colchis, ancient region at the eastern end of the Black Sea south of the Caucasus, in the western part of modern Georgia. It consisted of the valley of the Phasis (modern Rioni) River.