The Greeks conquered most of the known world
(which centered around the eastern Mediterranean) in the 4th century BC. That
opened up a lot of travel opportunities for the Greeks into
Mesopotamia. Just like all travelers, they
talked about the places they visited. That's how the list of
Seven Wonders came to be. The Colossus of
Rhodes was the last of the wonders created and the first to be destroyed, by an earthquake in 226/225 BC.
All seven wonders only existed at the same time for about sixty years.