The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A network of ancient Egyptian tombs built into the cliff face along the Nile.

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

The largest known Ancient Egyptian obelisk.

Ozymandias’ time-keeping temple.

Ancient Egyptian relief, claimed to depict an electrical light.

One of the most well-preserved temples of ancient Egypt.

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

The medieval center of the Islamic world was also once the seat of Saladin's sultanate.

In Egypt's expanding metro area, many of the neighbors are dead.

See gorgeous frescoes at this modest Byzantine place of worship.

This fortress dates back to the 6th century and is also the site of a controversial abandoned restoration project.

This statue of a 15th-century Hungarian military and political figure has become known for its resemblance to a particular cartoon knight.

This beautiful medieval Serbian monastery is home to frescoes, peculiar sculptures, and historical curiosities.

Stone age urban planning.

This 15th-century Serbian Orthodox monastery also contained a school for illuminating manuscripts.

A maze of underground tunnels beneath one of the most beautiful forts in Serbia.

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

Structure built from the skulls of vanquished foes.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

Mummies preserved naturally for seven centuries.

A patchwork of ruins from various civilizations in one of the world's oldest continually inhabited cities.

A monumental underground karstic wonderland is also the water source for over a million citizens of Beirut.