Meant to resemble a massive tree, the building is the best example of Spanish organicist architecture in Madrid.

Below the altar in Saint-Willibrord Basilica rests the mortal remains of Luxembourg's patron saint.

An artist-run shop filled with art inspired by and made from nature.

The severed head of a 17th-century Irish martyr lies within an intricate golden shrine.

The ancient tomb acts as a calendar that keeps perfect time.

This ancient Irish tower could easily have stood in for Rapunzel's prison.

A teddy bear sits on a chair watching the sunset from the mountaintop—just as the late Dan Clancy had done since childhood.

An ancient neolithic tomb that only sees the sun twice a year.

An eccentric garden of sculptures crafted in India decorate an Irish green space dedicated to Alan Turing.

An ancient chamber filled with wonderful rock art and a Neolithic carving of a human face.

Wallabies live naturally on this Irish island.

This 5,300-year-old tomb with mysterious carvings crowns an Irish mountain.

A corkscrew-shaped barn in Ireland.

A former fortified tower now houses a collection of classic communications equipment.

This Bronze Age tomb is the centerpiece of a clearing within a beautiful Irish forest.

A nun spent 16 years painting the stunning Celtic mural that covers the interior of this WWI memorial.

One of Ireland's most infamous prisons for rebels including men, women and children.

Dublin's "Dead Zoo" serves as a window to Victorian museum design.

These gigantic skeletons tower over visitors and provide insight into the creatures that once ruled over Ireland.

The enchanting archway is the only surviving portal into Dublin's lost medieval wall.

An Irish church where an 800-year-old mummy is reaching out of his coffin as if to shake hands.

The mummified heart of a saint lives on in this church—after a brief hiatus when it was stolen.

The chaotic studio of one of the 20th century's most important artists has been preserved down to the dust.