A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

An ancient Egyptian temple in the middle of Madrid, Spain.

A petite castle folly in the English countryside.

Museum about life, death, and cannibalism in the Stone Age.

A grandiose octagonal home crowned by a large dome stands out among the antebellum mansions.

The second-largest ceremonial mound in the United States is an artificial hill that is loosely shaped like a pentagon.

Bridge that died in war and was resurected.

An ancient knight and a symbol of the city's freedom.

The southernmost point in the United States is a beautiful place to look at but a deadly place to wade in.

These ancient sacred grounds granted amnesty to those who managed to reach them.

This black shoreline is made up of exploded lava particles.

This former Imperial summer home was the venue for a royal slap that once echoed 'round the world.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

The alleged house of the Virgin Mary is tucked away in a park and nature preserve on Mt. Koressos in Turkey and is holy to both Catholics and Muslims alike.

The ancient latrines of the Greeks, in all their public glory.

A marvel of Byzantine engineering under the streets of Istanbul.

Roman ruins top white travertine terraces formed by ancient hot springs.

After a profound show of devotion for his master, a dog becomes the symbol of loyalty for an entire nation.

The 10,000 Torii shrine.

This massive wooden building contains a giant Buddha, healing pillars, and tame deer wandering the grounds.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.