A trio of hidden hot tubs takes advantage of Iceland's natural geothermal vents.

The oldest bookstore in Iceland.

This tombstone marks the spot where the legendary British spy met his end.

This isolated structure beckons adventurers with sublime views of the Faroe Islands.

The largest lake in the Faroe Islands seems to be held hundreds of feet above sea level thanks to an optical illusion.

Legend says this rock spire is the finger of a witch who wanted to throw the Faroe Islands towards Iceland.

Located more than 600 feet beneath sea level, this tunnel boasts the world's first undersea roundabout.

This mysterious, medieval cathedral remains unbuilt but fiercely protected.

The last Victorian market in Belfast.

A museum marks and documents the site of the Titanic's launch.

This former church is believed to be one of the first Christian sites in Belfast Lough.

A Victorian marvel of engineering is now a 21st-century tourist attraction.

From Vikings to nationwide rebellions, this castle has seen its fair share of warfare.

The "Black Arch" guards the entrance to the picturesque Glens of Antrim.

Hidden in Carnfunnock Country Park is a lasting testament to the Normans who once settled in the region.

This rustic, flower-lined pathway once had very little in common with its namesake.

These unknown Bronze Age earthworks are believed to be ancient burial mounds.

This gnarled old tree supposedly sprouted from seeds kept in the pocket of a 16th-century Spanish sailor.

This castle once belonged to one of the most prominent families of medieval Carrickfergus.

It is said a heartbroken man visited the gap every day to stare blankly out at the sea.

This garden has existed for more than three centuries.

A brisk climb up this solitary peak leads to the origin story of a towering figure in Irish history.

Amazing vistas await visitors to this stretch of coastline.

400 million years of erosion shaped these fascinating seaside caves, which made an appearance on 'Game of Thrones.'