This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

A floating cat sanctuary on an Amsterdam canal.

Cat art as far as the eye can see.

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

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

Monasteries on rock pillars, once accessible only by frayed ropes.

David Sedaris called it "The greatest shop in the world."

The astonishing collection of an infamous criminologist.

This trail was once used to smuggle cigarettes, sugar, and other black market goods between Italy and Switzerland.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

The bones of some 7,000 soldiers killed in the historic Battle of Solferino are stored here.

A military museum, art park, mausoleum, and architectural oddity all on one fascist's estate.

On the shores of Lake Garda, the ruins of a Roman villa that allegedly belonged to the poet Catullus.

The skulls and bones of thousands of soldiers line the walls of this small Italian chapel.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

Thousands of well-dressed mummies below a monastery.

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.