Super-heavy Nazi architectural experiment.

This Nazi-built amphitheater was constructed on a sacred mountain site used by various German cults.

The 1936 Summer Olympics site is a crumbling remnant of sportsmanship and a history its host country would like to forget.

Silent memorial, using bone conduction to take people back to the Dresden Bombing of 1945.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

Ruins of a German Castle on top of a towering stone pillar.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

The studio built by fascists in the hopes of "reviving the film industry" with the occasional propaganda film opportunity thrown in.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

Bell tower juts out from a village buried under a lake.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

The famous sculptor left his mark on this Italian wall in an internationally protected example of street art.

Erected in 1697 this Philadelphia bridge is the oldest surviving roadway bridge and perhaps the oldest stone bridge in the United States.

This open air cathedral invites all faiths to worship under the only roof big enough to fit them all: the sky.

Henry Ford's failed rubber plantation in the middle of the Amazon rain forest.

An abandoned saucer-shaped monument in the Bulgarian mountains.

A submerged archeological park still holds the wonders of a Roman Sodom.

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

Centuries-old bridges grown from tangled roots.

The sound of swaying stalks in this stunning grove has been named a governmentally recognized sound.

Northern Ireland's Brobdingnagian stepping stones.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

Thousands of exquisitely carved stone water storage wells, hundreds of stone steps fill this exquisite medieval stepwell.