A pair of connected skyscrapers form this symbolic gateway.

For over 40 years, this quaint little house has teetered on a rock in the middle of a river.

Structure built from the skulls of vanquished foes.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

Romania's triumphal arch looks out over Bucharest.

This fairy-tale castle would make Dracula (who is said to have been imprisoned there) jealous.

A floundering Polish shipyard was once the soul of the Solidarity movement that capsized communism.

An impressive monument to Poland's independence.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

The Brutalist building harbors an unusual inverted dome that swoops down over its central sacred room.

This fortress dates back to the 6th century and is also the site of a controversial abandoned restoration project.

This museum housed in a former brothel explores the past and present of sex work in Amsterdam.

This cheese shop also houses a museum devoted to Dutch dairy.

A curious collection dedicated to human and animal anatomy and pathology.

Museum preserving torture methods from the past.

This virtually windowless mass of smooth concrete is the only Catholic church in the city.

This unique building in the main square stands out among the city's typically Baroque architecture.

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

This cathedral hides a sculpted dog that determines your fate and an unexploded shell from World War II.

Ancient ruins hidden underneath a modern luxury hotel.

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

The oldest inn in Kilkenny was established by the first convicted witch in Ireland.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

An ancient octagonal weather station named for the eight Greek gods of wind.