More people need to know that ancient Roman engineering was so precise, their aqueducts still produce clear water to this very day - 2,000 years later.
The secret to survival behind Nuremberg Castle's walls
A 50-meter-deep well carved into solid rock. In medieval sieges, secure water mattered more than thick walls.
Cologne Cathedral took 632 years to complete.
Construction began in 1248 and was finally finished in 1880, making it one of the longest building projects in architectural history.