Rome was the first city to reach 1 million inhabitants.
Today, Tokyo is the world’s largest city by population, with more than 37 million residents, but long before the Japanese metropolis took that honor, there was another record-holder: Rome. The ancient city was the world’s largest back in 133 BCE, when it became the first city to reach 1 million inhabitants.
Everyday life in ancient Rome was largely dictated by wealth: Affluent residents lived in finely decorated townhouses (and often had countryside estates for trips out of the city), while lower-income citizens resided in apartment-like buildings called insulae. But all social classes enjoyed the perks of living in a major city, including fresh water piped in from aqueducts, and the availability of markets, entertainment, and even food stalls that served quick meals. Rome’s population eventually declined as the Roman Empire fell, yet no city would surpass its record population for millennia — that is, until London became the world’s largest city, with 1 million people in 1800 and growing to more than 6 million people by 1810.
Modern human societies haven’t always gravitated toward city life — in the 1800s, only 3% of the world’s population lived in a metropolis. That changed with the Industrial Revolution, which drew large numbers of workers to cities, and today, 80% of Americans live in an urban environment, a trend that’s echoed around the globe and not expected to decrease. In fact, a United Nations report from 2018 predicts that two out of every three people will live in a city by 2050. Many of the globe’s busiest cities will continue to grow, and some will become megacities — areas with more than 10 million people — creating the potential for some cities to become more important than countries, changing maps and impacting economies.
