The first tunnel to be dug beneath a river, repurposed as an art and museum space.

A network of concealed passageways lies within a busy London Underground station.

One of the largest collections of merchandise from the famous British sci-fi show can be found smack in the middle of Indiana.

The weathered grave of a medieval anchoress who walled herself up in a cell attached to a church.

Ireland's most remarkable collection of these curious cone-shaped houses is worth the buzz.

The highest peak in Northern Ireland is topped with a stone tower and haunting burial mounds.

The inscribed stone at Kilnasaggart is a remnant from nearly a millennium ago.

The largest portal tomb in Europe has a capstone weighing around 150 tons.

A mysterious Neolithic tomb is perched along the edge of a modern golf course.

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

It's possible to walk inside one of the largest Neolithic tombs in Britain.

The highest peak in Wales is said to be the final resting place of a giant killed by King Arthur.

The stately remains of Llywelyn the Great's mighty fortress.

The remains of centuries of copper mining appear like an alien landscape.

A deserted Bedouin village lines the shores of this stunning desert oasis.

Go back 50 years with a turn on one of the park's carefully restored vintage fairground rides.

A spiral staircase connects the limestone cave with Pembroke Castle, birthplace of King Henry VII.

A 600-year-old mini shrine guarded by a sword-wielding knight hides in a crumbling cliff face.

More than 5,000 contemporary and "historic" mustards from around the world.

Legends say that this small island was the final resting place of the Welsh saint of lovers.

A harem-inspired Moorish fantasy design in a Victorian-era Welsh castle.

Stroll through Welsh history in a village of reconstructed structures.

Quirky Welsh observatory unites art and science.

A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.