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

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

Petrified footprints of one of the very first vertebrates to walk on land.

Modern sundial uses ancient methods to tell time and date perfectly.

A meandering boardwalk across the bogland leads to a "stairway to heaven" with sublime views.

One of Ireland's best-preserved chambered cairns can be found next to a wishing tree.

The remains of this deep, dark mine have left behind a haunting rocky warren of tunnels.

The oldest pub in Ireland may also be the oldest surviving bar in the entire world.

A moody and picturesque riverside ruin overgrown with vegetation.

A strange egg in a mucky bog of western Ireland marks the spot of an aviation milestone.

A stunning Victorian abbey and walled garden on a lakefront.

Achill's most recently abandoned village dates back to to the Age of Enlightenment.

This medieval footbridge in the Swiss Alps is known to attract cliff-jumping daredevils.

The Sighignola summit on the Swiss border offers views so breathtaking it's been named one of the most beautiful places in Italy.

The ghostly remains of a gunpowder mill lost in 70 hectares of thick woods.

Two monstrous faces loom over a village in Czechia.

A geothermal energy project gone wrong is fracturing the city's picturesque architecture.

The largest of only eight working transporter bridges left in the world.

Go deep down into the earth to experience the world of Welsh coal miners.

The remains of one of Wales’ great medieval buildings, with a pub in the cellar.

Following years of secrecy, the hidden history of a World War II site is being brought to light.

A look into the life of a Victorian-era prisoner.

A prison with a more than 200-year history.

The remains of a 13th-century stronghold built by the Welsh prince known as Llywelyn the Last.