Rodrigo Cervantes/KJZZ

A view of Madero Street — in downtown Mexico City — one of the streets with more pedestrian traffic in the country.

Across the globe, more and more people are moving to cities. Current estimates suggest more than half of the world’s population lives in cities, with that number expected to rise.

Monica Smith, a professor at UCLA's Institute of the Environment and Sustainability, argues that many of the fundamentals of cities themselves are basically the same as they were several thousand years ago.

In her new book "Cities: The First 6,000 Years," Smith writes that ancient cities and modern ones, in many ways, are very similar.

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