The first river valley civilization was Mesopotamia, located in Asia. Asia has had the most river valley civilizations.
Danube River Valley
lakes
Tigris, Euphrates River Valley's and Los Angeles
Huang He - China Nile- Egypt Indus- Pakistan
yellow river valley
its location limited its contact with other advanced cultures ;) (C)
Greece was not centered around a river valley.
Democracy
The Nile River was the axis of two early African civilizations
Vast Empires
They had to sale the slaves from africa in order to get more gold and more food in order to survive