Location near a waterway contributes to the spread of ideas as it provides easy access to transportation.
Explanation:
Waterways were considered to be the fastest means of transport before the invention of motor-vehicles and flying. It was a reliable route for travelling and carrying goods to long distances.
It is for this reason that most ancient civilizations and societies settled near waterways. It provided them access to transportation of humans and goods.
Thus, societies that lived near waterways could spread their ideas and other cultural practices to other societies as waterways provided them easy access to travel far and beyond to new places.