One of Amsterdam's narrowest houses is located right across the canal from its widest.

Seven mini rowhouses fill the gap between 54 and 70 Westerstraat.

This unattributed sculpture in Amsterdam is hiding in plain sight.

A beautifully eclectic mix of architectural styles.

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

Museum preserving torture methods from the past.

The commemorative stone column conceals a secret laboratory.

This striking statue brings a scene from the African savannah into central London.

The medieval woodcut-style artwork chronicles life in medieval London.

This unique bridge curls up like a caterpillar to let boats pass and then unfurls again to span a small canal.

A tiny replica of the iconic London landmark hides on the side of the steel structure.

An architectural oddity hides in plain sight on this iconic London bridge.

Revel in the Victorian splendor of the world's oldest eating establishment inside a museum.

These morbid carvings remind churchgoers of the inevitability of death.

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

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

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.

The fierce beast perches atop a pedestal marking where the historic City of London gates once stood.

A little slice of Japan and its aesthetics in London's Holland Park.

19th-century scientists would make the pilgrimage here to verify the precision of their measuring sticks.

Bronze sculpture celebrating the relationship between Churchill and Roosevelt.

A statue marks the exact spot where The Boy Who Never Grows Up made his first literary appearance.

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

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.