This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

This unattributed sculpture in Amsterdam is hiding in plain sight.

This impressive collection of rare books on ancient mysticism inspired author Dan Brown.

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

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

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

A floating cat sanctuary on an Amsterdam canal.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

The world's only museum devoted to the wonders of fluorescence.

This was once a hall in which a 16th-century royal banquet was hosted by King James VI of Scotland.

A labyrinthine network of chambers with a storied past hides below Edinburgh's South Bridge.

This 16th-century house tells the city's history through old artifacts and quirky tales.

An American ghost town hides along a side street in Scotland's capital.

This historic pub has maintained much of its 1906 decor, including a small sequestered room for women, where orders were slipped through a tiny window.

This otherwise ordinary close on the Royal Mile constituted the end of the world for Edinburgh’s poorest residents.

Every birth, death, and marriage is recorded in these color-coded leather-bound books.

This allegedly haunted 16th-century tower house-turned-museum exhibits thousands of spectacular objects.

Near the former site of numerous witch burnings, this lavish Edinburgh mainstay pays homage to Scotland's brutal history.

Protecting the dead from opportunistic body snatchers.

Summer in Scotland begins with a spectacularly wild and colorful event rooted in ancient pagan traditions.

A bit of the Berlin Wall was gifted to the Icelandic capital to commemorate the 25th anniversary of German reunification.

The strange, ritualistic-seeming 100+ year old basement of a New Hampshire undergrad society.