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

Certain traditions prevail on the least-visited island of the Aran Islands.

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

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

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

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

This ancient Irish religious site is covered in ancient carvings, many of which have barely aged.

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

One of the most popular megalithic sites in Ireland stands as a humbler version of Stonehenge.

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

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

The carved medieval stones stand near the ruined abbey's parking lot.

A poignant memorial shows the widows and children left heartbroken by the worst fishing disaster in Scottish history.

The United Kingdom's smallest working cathedral also serves as a quaint bed and breakfast.

Summer in Scotland begins with a spectacularly wild and colorful event rooted in ancient pagan traditions.

This observatory within Europe's first dark sky park offers stunning views of the night sky.

A historic cave in Scotland once served as a hiding place for a famous Covenanter.

This tin chapel was built by POW's during World War II and is painted to look like something much more grand.

An 18th-century lighthouse built on a 16th-century castle is now a monument to the maritime beacons of Scotland.

Every birth, death, and marriage is recorded in these color-coded leather-bound books.

The mysterious megaliths have enchanted and intrigued visitors for thousands of years.

Small museum dedicated to the founder of electromagnetic theory.

These mysterious religious carvings were once thought to be thousands of years old but are actually the work of modern eccentric.

Remnants of the 16th-century defensive wall still stand unassumingly within Edinburgh.