Which cities were very prosperous and developed in ancient times, but the modern era had declined? What causes it?

Antioch. The four great cities of the Seleucid Kingdom in Syria, Antioch, Seleucia, Apamia, and Laudisia. Except for the last one, all the other three were declining. Let me only talk about Antioch here.

After Seleucid was conquered by Pompeii, Antioch continued to serve as the capital of Syria under Roman rule, even more eye-catching than before under the Greek rule. Antioch connects the Mediterranean basin and the Mediterranean, and there are mountains in the northwest and southeast directions, with only one valley between the mountains extending towards the sea in the southwest. Thanks to this geographical advantage, Antioch is the most important transportation hub in the entire East.

According to Strabo's records, Antioch is divided into four parts, and the Seleucid palace is also located here. "In terms of the area and strength of Antioch, they are comparable to that of Alexandria and Seleucia on the banks of the Tigris." In the lower reaches of Antioch, the two satellite cities, Daphne and Seleucia, are located betwee...
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