The valley of the Eurotas is a natural fortress , bounded to the west by Mt .
Ancient Sparta was built on the banks of the Eurotas River , the main river of Laconia , which provided it with a source of fresh water .
The valley of the Eurotas River is a natural fortress , bounded to the west by Mt .
Ancient Sparta was built on the banks of the Eurotas River , the main river of Laconia , which provided it with a source of fresh water .