It's been more than 2,000 years since the Romans built a network of famously straight roads connecting major cities – and they still have an impact today.
The roads, which were constructed to transport troops to the outer edges of the Roman empire, correlate strongly to prosperity today, researchers have found.
Using satellite images of light – a way to estimate economic activity – scientists discovered that the 2,000-year-old road network correlated to areas of contemporary wealth.
Ola Olsson, professor of economics at the School of Business, Economics and Law at the University of Gothenburg, said: "Given that much has happened since, much should have been adapted to modern circumstances.
"But it is striking that our main result is that the Roman roads have contributed to the concentration of cities and economic activity along them, even though they are gone and covered by new roads."
The Roman road networks were impressive constructions, which at their peak numbered 49,000 miles of highway.
They were not built for economic reasons, and little consideration was given to older road networks or to villages and communities along them.
Nevertheless, the Roman roads soon began to be used for trade and transport, becoming links between emerging market towns and becoming important for economic development.
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The researchers superimposed maps of the Roman Empire's road network on top of modern satellite images showing the light intensity at night.
They then divided the map into a fine-mesh grid, in each box measuring the presence of Roman roads and comparing it with the infrastructure, population density and economic activity of today.
Olsson said: "What makes this study extra interesting is that the roads themselves have disappeared and that the chaos in Western Europe after the fall of the Roman Empire would have been an opportunity to reorient the economic structures.
"Despite that, the urban pattern remained."
Another factor that supports the study's findings is what happened in the eastern parts of the Roman Empire, in North Africa and the Middle East, where wheeled transport was basically abandoned in the fourth to sixth centuries to be replaced with camel caravans.
Those roads were used less and less and were allowed to fall into disrepair and, in contrast to the western parts of the kingdom, new roads were not built on top of the old ones.
Olsson said: "The roads became irrelevant and thus we don't see the same continuity in prosperity at all.
"It can be said that the area was affected by what is called a 'reversal of fortune' – countries that early on developed civilization, such as Iraq, Iran and Turkey, are today autocratic and have significantly worse economic development than countries that were then in the economic periphery."
Olsson said the results may also be important as a background for modern-day political infrastructure decisions.