Subject: Historical cities

Machu Picchu, Peru

One of the most popular ancient cities in the world.

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Nearly 8,000 feet high in the Andes, the Incan citadel of Machu Picchu retains an aura of mystery and majesty even as it welcomes thousands of tourists a day.
When the Spanish conquered Peru, Machu Picchu's very existence was kept secret from them.
The vast complex was revealed to the outside world in 1911, and quickly became the emblem of Incan achievement.
Built more than 500 years ago with drystone construction, the city sits on the saddle between two peaks rising above tropical jungles.
Clouds swirl among the ruins, whose significance remains largely unknown.
Terraces and ramps skirt the mountains, and the buildings appear to reflect the Inca's sophisticated grasp of astronomy -- though archeologists are still seeking to understand exactly how.
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Athens, Greece
Athens traces its origins back 5,000 years, but the modern city has found remarkable ways to coexist with its iconic ancient monuments.
Below the Acropolis, walkable neighborhood streets wind past cafes and shops.
Many brim with tourist tchotchkes, but with enough art galleries and good eating mixed among them even the most jaded traveler will be satisfied.
Much of the city's social life centers around the monuments, turning the stunning ruins of classical Greece into casual backdrops of Athenians' every day lives.
Petra, Jordan
While the ancient city of Petra is simply a famous archaeological site to most of the world, for university professor Sami Alhasanat, it's home
This region between the Dead Sea and the Red Sea has been inhabited since the earliest days of humanity, but around 300 BC the rulers of the Nabatean Kingdom laid their claim to cultural greatness by carving magnificent buildings into red sandstone cliffs.
Gorges and canyons surround the ancient city, creating a maze of passages that helped keep it secret from Europeans for centuries.
Adding to the mystique: no cars are allowed in the ancient city.
Visitors who don't want to walk have to hire a camel, donkey or carriage to get around.