Cities have been critical in human development for almost 10,000 years.

We looked at thousands of years' worth of data to determine the 16 greatest cities in human history.

Each entry on the list was a center of commerce, technology, and innovation, from ancient Jericho to modern-day Tokyo.

Cities have played a crucial role in human development for more than 9,000 years.

From Jericho, the oldest known city in the world, to Tokyo, the largest city today, cities have served as centers for commerce, technology, education, and culture.

And cities are continuing to grow to new heights. In 1960, there were two rural dwellers for every city dweller in the world. But as the biggest wave of urbanization in human history continues, more than half of the world's population now lives in urban centers.

We looked at data spanning thousands of years to compile this list of the greatest cities of all time. Although determining the exact population of ancient cities is no easy task, we used research from historians Tertius Chandler and Gerald Fox in their book "3,000 Years of Urban Growth" and political scientist George Modelski's 2003 book "World Cities, -3,000 to 2,000."

The numbers were drawn from the size of a city's military in peacetime and in war, household data, agricultural commerce, church records, fortification sizes, food distribution, loss of life in a disaster, and city comparisons.

Read on to see the 16 greatest cities in human history: