What does "steeped in" mean here in this context?
The heart of Asia is where civilisation was born. In ancient Mesopotamia along the banks of the mighty Tigris and Euphrates Rivers and steeped in the Indus Valley stood the very first towns and cities known to mankind.
Edit: It's from "The Silk Roads: A New History of the World-Illustrated Edition" by Peter Frankopan. It's the simpler version that targets older children.