4. Beginning in the 4th century B. C
Beginning in the 4th century B.C., Romans constructed huge aquaducts to carry water for distances up to 50 miles.

6. These structures were built on continuous gradual declines to transport water by force of gravity. Each arch spanned 82 feet.

10. Roman
The Colosseum
A.D.70-82
Rome, Italy

12. Originally called The Flavian Amphitheater after the Roman Emperor Flavius

14. The Colosseum seated 50,000 spectators.
It was so efficiently laid out that it inspired present day stadium design.

24. Roman
The Pantheon
A.D
Rome