A paradeisos was a hunting reserve or pleasure-ground for the nobility of the Achaemenid (Persian) Empire, normally a walled-in area with groves of trees, wild animals, and running water.
Triparadeisos was the place where the Treaty of Triparadisus occurred, in which Alexander the Great's Empire was divided between his generals in 321 BC.
Ancient Heliopolis -named Triparadeisos- initially formed part of the Diadochi kingdoms of Egypt & Syria.
The population -probably nearly 15000 inhabitants- was mainly local in the second century under Hadrian with a few descendants of the Roman colonists and likely varied seasonally with market fairs and the schedules of the caravans to the coast and interior.
The present Temple of Jupiter (the biggest in Antiquity) presumably replaced an earlier one of Triparadeisos using the same foundations.