Op-art architecture designed for happiness.

The house that took a plunge into the facade of a museum.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

The only museum with its curator—and her pets—buried inside.

A whale rib was used to advertise the store by the arch that offered exotic goods from far away.

Every inch of this chapel is covered in craftsmanship from across the world.

Cave shrine on Monte Pellegrino.

Thousands of well-dressed mummies below a monastery.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

An ancient Egyptian temple in the middle of Madrid, Spain.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

Cold war icon and onetime "hole" in the iron curtain.

The most visited, and possibly most controversial, museum in Germany.

A fascinating insight into daily life in the Eastern Bloc.

A statue in the center of Dublin dedicated to one of their favorite sons of rock & roll.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

The modern birthplace of Irish freedom.

A six-ton wedding present for the King of the Scots.

A 18th century graveyard and its astonishing cortege of macabre iconography.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

The world's oldest bookshop still in operation.

A site where “the ravages of the war are more striking…than any other place in contemporary Spain.”

This Arabesque Italian castle was built with a primitive, if ingenious, air-conditioning system.

When this funny little building went up in the 19th century, most people thought it would simply fall over.