A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Literal "money laundering."

A clone of a cloned tree that was so important it allegedly had its own guards.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

This unassuming passageway played a key role in one of the most important events in U.S. history.

Coins and medals straight from the mint await visitors to this shop in the nation's capital.

This fountain of a little boy that spits on passersby at erratic intervals is a town icon.

Every half hour the eye-rolling clock face sticks out its tongue to mock the good citizens of Koblenz.

This unattributed sculpture in Amsterdam is hiding in plain sight.

A set of seven houses, each built in a style that represents a European country.

Inside the Wayne County airport is an amazing collection of lights and sounds.

The largest bell in the world has been swinging high above a Cologne cathedral for almost a century.

Thousands of tourists and residents in Cologne affix "love padlocks" on the Hohenzollernbrücke Bridge to symbolize their affections.

This small condiment museum makes all manner of mustards with a 200-year-old mill.

Some 80,000 Delft Blue tiles line the inside of this Amsterdam walkway.

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

Famed for its pie, this eatery has a hidden tunnel that allowed Catholics to secretly walk to church during the Reformation.

A floating cat sanctuary on an Amsterdam canal.

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

A surrealist timepiece by the artist of melting clocks.

The narrowest street in Paris.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The very center of Paris is surrounded by a bevy of strange good luck rituals.