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

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

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

This luxury shopping lane has been protected by its own tiny police force for over a century.

Lovers proclaim their unbreakable bond by leaving their names on locks fastened onto the Shoreditch fence in East London.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

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

London's smallest police station is barely the size of a phone booth.

An unusual round church in London with a Templar past.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

These subterranean models show Mexico City's central square during three different eras.

This museum houses two of Mexico's most impressive Aztec monoliths.

This clock was gifted to Mexico as a show of gratitude for its long history of welcoming Arab migrants.

A close look at the church's walls reveals pieces of Mexico's history.

The official Presidential Residence of Los Pinos became an emblem of Mexico's opulence and presidential corruption.

Mexico City's residents are being watched by this state surveillance headquarters, designed by architects with a flair for intimidation.

The turquoise-studded skull of a long-dead Aztec man sits within Mexico City’s Museum of Anthropology.

Come face to face with the ferocious visage of the serpent-headed mother goddess of the Aztecs.

This Aztec structure remained hidden until the demolition of a supermarket exposed the lost temple.

Inside a busy metro station, an impressive mural depicts the prehispanic city of Tenochtitlán.

These spectacular, symbolic serpents lie within the shadow of the Great Temple.

This ancient jade mask depicting the Zapotec bat god was found in the ruins of the pyramids of Monte Alban.

A barbarous band of serpents guard the bases of these Aztec temples.