This hole formed by a glacier is the largest and best-preserved of its kind in Stockholm.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

This uniquely designed bridge served as the city gate for Comacchio.

This 16th-century monastery was founded to cloister the daughters of wealthy local families.

A volcanic old faithful, Stromboli has been erupting continuously for the last 2000 years.

Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

Amid the rubble of Aleppo's Old Quarter, part of a historic market has been restored and re-opened.

What is left of the pillar of Saint Simeon, the voluntary martyr who climbed the column to give his sermons, remaining perched there for thirty-seven years.

One of the oldest and largest castles in the world.

This Roman amphitheatre was also the location of the first gladiator school.

The underground sanctuary of a mysterious ancient Roman religious cult contains an exquisite traditional fresco.

Numerous stone coffins from different centuries, lined up in a sixth century basilica.

Also known as the Temple of Poseidon, this is one of the best-preserved Greek temples in the world.

An ancient Phoenician citadel once stood at the site where Queen Dido first landed, according to legend.

The largest and best-preserved Roman amphitheater in Africa was designed to seat 35,000 people.

This ornate mosque is said to hold the remains of Muhammad's granddaughter beneath its dome of pure gold.

Mysterious lost empire of the Silk Road.

This lovely, if imposing, piece of Canadian gothic is possibly the most photographed hotel in the world.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

A former fisherman's hut deemed too small for habitation is now a delightful tourist draw.

Look closely and you’ll notice that the color changes a third of the way up the tower.

Fragments of architectural wonders from around the globe are embedded in the newspaper building's walls.

One of its engravings is believed to be among the first representations of medical and surgical instruments.