This town named for the ancient God of War is home to fewer than a thousand people, but it's the birthplace of the Greek Revolution.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

Scattered throughout London are ancient remnants of the city's former bounding wall.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

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

Frida Kahlo's childhood home, now a museum of her life and works.

The final resting place of the great navigator, or maybe his brother.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

This underground church is topped with a 500-foot cross that is seen by many as a beacon of fascist hubris.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

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

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

Macabre astrological automaton clock dating to the late 1400s.

The attic of a four-century-old canal house hides a clandestine church.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

The ghostly remains of an accidental sea.

The "3rd largest" city in California is an empty mirage of suburbia in the middle of nowhere.

Abandoned hotel with adjacent lake and golf course.

Oldest building in California still in use.

Megachurch turned Catholic church comprised of 10,000 glass panes.

Bug-devouring flora are the stars of a special wing of the glass conservatory.

This former stomping grounds of the most eminent astronomers of the early 20th century.

An extraordinary final resting place full of oversized art, amazing statues, and dead celebrities.