Real bones which are said to have belonged to a Polish dragon.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

An underground city of salt.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

Huge standing stones mark a site of megalithic mystery.

This single room has survived the centuries with almost no deterioration.

Wallabies live naturally on this Irish island.

After being destroyed by IRA sympathizers, the ruins of this stately Irish manor have sat vacant for decades.

A moody and picturesque riverside ruin overgrown with vegetation.

An 1814 castle that hosts an exhibit of "explorabilia".

This controversial Irish show cave is home to a massive formation known as the Great Stalactite.

The world's toughest modern Christian pilgrimage leads directly to the gates of Hell.

The oldest public library in Ireland.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

The comedy and tragedy of Oscar Wilde is preserved in a Dublin park, captured in a sculpture of colorful stone.

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

A corkscrew-shaped barn in Ireland.

A sacred well steeped in Pagan roots on the West Coast of Ireland.

An unusual manor of stunning beauty, born out of a crippling disease.

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

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

A remarkably intact castle that once was the largest in Ireland.