Most of the big cities found in Asia, Europe, North America and parts of Africa are located on the banks of big rivers. This is due to the fact that the cities began as villages, then towns near major rivers so as to guarantee supply of water. You’ll also have noticed that the big cities have landmark bridges over such big rivers. Nairobi is not blessed with big rivers - or bridges - but instead, it has a maze of smaller rivers and streams, collectively referred to as the Nairobi River Basin.