Eduardo Kobra’s breathtaking 32,300-square-foot graffiti wall took over Rio’s Olympic Boulevard.

This massive Brazilian church is built like an angular, technicolor pyramid left by Mayans from the future.

A 125-meter long "tribute to the Brazilian people."

The ritual has been performed uninterrupted for nearly 700 years.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

A mysterious pair of mice eating a piece of cheese is London's smallest public sculpture.

Only a few pieces remain of the structure that carried people and goods across the Thames for some 600 years.

The 2,000-year-old beam is tucked within the pedestrian entrance to the old London Bridge.

The commemorative stone column conceals a secret laboratory.

The Great Fire of London and the regulation of one-way streets both started in this alley.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the first ‘Harry Potter’ film.

This London marker celebrates the spot where the world-famous English band was founded.

One of America's founding fathers lived in this London lodging between 1757 and 1775.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

An unusual round church in London with a Templar past.

One of the few remaining examples of 19th-century London’s attempt to clean up its reputation.

This inn of the court provides a fascinating window into London’s legal and architectural history.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

One of corporate America's best-kept secrets is also one of the most publicly displayed.

Unruly residents were housed in this one-person cell until the Black Maria arrived.

An underground magnet for ever-changing street art.

This enormous monument is one of the most iconic structures in Tokyo, rudely nicknamed "The Golden Turd."