Only a handful of these gorgeous historic waterwheels remain but even those are in danger from local unrest.

Mysterious lost empire of the Silk Road.

Magnificent Roman ruins lie vulnerable to destruction on the edge of the Mediterranean.

This triumphal arch is the only fully standing structure that remains from Roman-era Oea.

A fortress-like granary that has been continually in use for more than nine centuries.

The world's most active stratovolcano is almost always erupting.

This amazingly preserved Doric temple was abandoned before it was ever completed.

This curious, round temple is the oldest still-standing marble building in Rome.

The yawning maw of this pagan visage is said to bite off the hands of liars.

2300-year-old Roman road connecting the empire.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

Now an entertainment complex, the Lingotto building was once an avant-garde auto factory with a test track on the roof.

A fake medieval village in the middle of Turin.

This bustling Italian plaza is built on the ruins of an ancient Roman amphitheater.

The only visible reminders of an elaborate engineering project that kept the tower from reaching the tipping point.

The National Railway Museum in York is the largest railway museum in the world, attracting almost 1 million visitors per year.

The little-known second castle that William the Conqueror built in York.

The final resting place of England's most notorious bandit.

One of the shortest streets in York has an especially odd name.

Follow the original medieval paths that wind through this intriguing section of the city.

This medieval church is not only notable for its architecture, but also its connection with LGBTQ+ history.

This network of narrow, medieval passages has the most delightful name.

This sculpture marks the spot where one of the greatest Roman rulers was proclaimed emperor.

This memorial to World War II's fallen airmen shows us the movements of the stars that once guided them.