<span>Early civilizations lacked the
expertise needed to construct the elaborate works necessary to modify
the land for their own use, such as massive irrigation systems or graded
tunnels and roads to pass through natural barriers. The earliest cities
were established in geographically beneficial areas, providing their
citizens with ready access to the natural resources they needed. Egypt,
for instance, enjoyed a massive agricultural benefit from the regular
flooding of the Nile River, as well as protection from other
civilizations created by the deserts and harsh terrain that surrounded
the kingdom. Rivers and sea currents provided established trade routes
between these civilizations and encouraged trade, while mountains acted
as cultural barriers and allowed the people on either side autonomy from
one another. Later civilizations learned to take advantage of geography
to suit their needs, allowing for colonization of areas previously
unsuitable for human habitation.</span>
