What factors unite the nation of european union

One of the main factors that unites the different nations of the Europe into a single "Eurozone" is an economic one. It is much easier for all nations to have a single currency than for each nation to have its own. This was a major unifying factor.

Humans have survived and thrived in mexico city by using technology to create greater access to land. when the spanish conquered the aztec capital, tenochtitlan, in the 16th century, they built mexico city by draining the lakes and filling in the lake water to create more arable land for agriculture. this technique of land reclamation has continued to be fundamental to human civilization in mexico city.