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

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 unique work of automotive art calls this shopping center home.

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

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

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

Something's missing between the arcades of the Palazzo della Ragione in "the city of the three withouts."

One of the world's oldest working clocks is curiously missing the Zodiac sign of Libra.

A complex, nine-layer maze on the grounds of a Venetian doge's playground.

Hidden in an Italian forest is a completely homemade amusement park that has taken a lifetime to create.

A star-shaped fortress town fort built in the geometric model of the Renaissance utopian city.

A tiny church on a man-made island in the Adriatic.

A curious little museum dedicated to the furry feline in the cat haven that is Old Town Kotor.

A wonderfully strange collection of 500+ stuffed frogs doing people things.

Croatia's "hairy stone" fortress is one of the most well preserved Istrian castles.

A forgotten monument to Yugoslavian freedom.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

During World War II, this rice mill became a Nazi concentration camp.

A miniature train-ride through Slovenia's largest cave system.

The remains of a sunken military ship wreck visible through clear water.

The only gulag ever to exist in socialist Yugoslavia.

This truly palatial work of Communist-era architecture now sits crumbling on a Croatian beach.