These gutted monastery ruins still stand proudly in the middle of the Italian countryside.

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

A medieval fountain lined with 99 unique stone faces whose origins and meaning remain unknown.

Geothermal waterfalls in Tuscany.

A Jenga-style cylindrical tower of books that appears to go on forever.

Two stunning 17th-century libraries and a cabinet of curiosities.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Nightmarish example of the unintended consequences of weapons testing.

Legend has this precariously placed rock was placed by giants. Science has another explanation.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

This former Masonic lodge has been transformed into part museum, part bar, all awesome.

The first Russian Orthodox church in the Catholic city of Rome in almost a thousand years.

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

These quaint French houses dangle precariously over a precipice.

An unsettling shrine dedicated to the ravenous beast that prowled 18th-century France.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

A Gothic cathedral created from volcanic rocks.

An industrial site turned into Hungary's most cherished natural wonder.

The second-largest Jewish temple in Bulgaria was deserted after World War II, seized by the communist government and then abandoned again.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

This abandoned secret city is a crumbling wonderland of Soviet ruins.

A 16th-century horror show built in a lovely Italian garden.