Hidden well off the beaten path in Catalonia is this crumbling medieval castle that is slowly being covered in graffiti.

These overlooked ruins give an intimate look at the Inca Empire's urban planning prowess.

These mysterious 1,000-year-old walls have revealed little about their past.

Over a millennium ago, this site on the shores of Lake Titicaca was home to a city of more than 10,000 people.

Once the foundation for a mansion, these ruins now offer amazing panoramic coastal views.

A collection of sculptures that explore what's at stake when nature is thrown out of balance.

The first piece of public art dedicated to LGBT rights.

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

A Manhattan office building is home to the world's largest chess board.

The most confusing clock in New York.

This lavish room at NYC's French Embassy is a rare relic from the end of the Gilded Age.

Commemorating the spot where the famous scientist fed his pigeons.

Have a steam and some blini at this cafe in a century-old bathhouse.

The former hotel where Tesla invented the radio.

An annual extravaganza of Broadway theater memorabilia.

Avoid gangster interaction while window-shopping.

This interactive gallery makes you feel like you've stepped into a fantasy world filled with whimsical monsters.

Deep under Manhattan is the largest construction project in city history. So far, the project has taken the lives of 23 workers, or "a man a mile."

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

Manhattan's lighthouse, erected at the insistence of the unsinkable Molly Brown.

“Invented in Key West, Perfected in Brooklyn."

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

New York City's smallest piece of private property.

Read a book next to a Midtown waterfall.