[bright string music]
- Rick Steves: As Rome expanded, they built elaborate waterworks,
aqueducts you can see to this day,
bringing fresh water into the great cities of the empire,
to Nimes in France,
Segovia in Spain,
and, of course, into the city of Rome itself.
Water infrastructure was a Roman engineering forte
and vital for the empire.
The Pont du Gard in southern France
is just one of many ancient aqueducts
surviving across Europe.
They heralded the greatness of Rome,
reminding the far-flung empire's subjects
how fortunate they were to be on the winning team.
This perfectly preserved Roman bridge supported a canal
or aqueduct on the very top.
The Pont du Gard was a critical link,
helping keep a steady river of water flowing across country
and across this river.
Remarkably, it was engineered
so that the water dropped only one inch
for every 300 feet for 30 miles,
harnessing gravity to flow all the way to the city of Nimes.
A chance to walk through the top level shows how it all worked.
This is what Roman aqueducts were all about.
This is part of a 30-mile-long channel.
A man-made river flowed through this for 400 years.
You can still see the original stones,
a thin layer of mortar that waterproofed the channel,
and, after centuries of use, a thick mineral buildup.
The Pont du Gard's main arch is the largest
the Romans ever built.
The bridge itself has no mortar, just ingeniously stacked stones.
Taking full advantage of that Roman specialty,
the round arch,
the structure is held in place by gravity.
Simple as it may seem, the round arch was key
to Roman architectural greatness.
Previous structures were limited by two vertical posts
spanned by a lintel, which was structurally weak.
A round arch could span a much wider gap,
and once the central keystone is placed,
the arch can support just about whatever
you want to build on top of it.
Without the round arch,
none of Rome's greatest structures
would have been possible.