Modern "global cities" inspired by patterns in the Middle Ages

In an article for Der Spiegel Parag Khanna, director of the Global Governance Program at the New America Foundation in Washington discusses how the current transition process toward global governance began in the rise of Europe's city states during the Middle Ages.

Khanna writes:

First let us take a step back and see how the global landscape has already come to resemble a crucial period of European history, namely the Middle Ages. It was a long and uncertain period, and thus an ideal metaphor for our times. It was an age of plagues and progress, commercial revolutions, expanding empires, crusades, city-states, merchants, and universities. The new middle ages -- synonymous with our postmodern globalization age -- have already begun.