This overlooked street light once served as a KGB dead letter box.

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

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

An unusual ode to the late Irish playwright, complete with a squiggly bust and coffin-shaped bench.

A living memorial to the trees London lost during the Great Storm of 1987.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

A plaque marks the underground site of one of London's "lost rivers."

The rose garden in Regent's Park where Pongo and Perdita met for the first time in Disney's "101 Dalmatians."

A measuring mishap led to these artificial stone ladies losing their stomachs.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

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

The last of Amsterdam's original sea level markers remaining in place.

This large copper bolt represents the benchmark for measuring sea levels in most of Europe.

A succinct inscription commemorates the ebb and flow of a woman's life.

A curious urban windmill once owned by a renowned British mathematical physicist.

The bust of Romania’s most notorious ruler, Vlad Dracula aka "Vlad the Impaler," keeps watch over the ruins of his medieval court.

One of the most controversial statues in Romania is an emperor with no clothes.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

This once-derelict building is now one of the most beautiful bookstores in the world.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

An abandoned canal route lies hidden under the streets of Manchester.

Stonehenge has nothing on Castlerigg’s views.

A theatre built to house the rowdy Oxford graduation ceremonies became the stage for a debate about God's existence.