Ancient ruins hidden underneath a modern luxury hotel.

An ancient Egyptian obelisk is now used to commemorate fallen Italian soldiers.

A plaque immortalizes the spot where the early American spy said his famous last words: "I only regret that I have but one life to lose for my country."

The site of the deadly Triangle Shirtwaist Factory Fire.

Da Vinci's equestrian statue, 500 years in the making.

Built to repay the sins of the father, this church is home to one of the most valuable works of Western art.

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.

Go inside to really appreciate this 500-year-old technological masterpiece.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

2300-year-old Roman road connecting the empire.

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

Thousands of well-dressed mummies below a monastery.

The middle finger of modernity.

This community on a small Venetian island has taken to painting their houses in bright neon hues.

Architectureal fantasy quarter of Rome.

This abstract sculpture is rumored to cast a hammer-and-sickle shadow once a year.

A layered tribute to the work of mosaicist Isaiah Zagar.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

This historic building housed the surviving crew members of the Titanic, who were left destitute after the wreck.

Discover the taste of mold.

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

This former crime corner has been turned into an eclectic community center.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

The most confusing clock in New York.