The patches of trees pay tribute to Queen Elizabeth II.

A headstone notes where the most famous of Robin Hood's legendary Merry Men is reportedly buried.

This petite cutlery factory sits on the foundations of a defunct gasworks.

A museum dedicated to the tragedy of Bloody Sunday.

A massive Celtic cross secretly growing in an Irish forest.

These murals stand as reminders to the troubled history of this Northern Ireland city.

This Irish church has a striking circular design inspired by the ancient Grianán of Aileach.

You can see three Irish counties from this Neolithic hillside fort, once the seat of the Kingdom of Ailech.

This tiny train shuttles passengers to one of Northern Ireland's most spectacular sights.

Northern Ireland's Brobdingnagian stepping stones.

Originally commissioned as a sculpture to reflect the history of Belfast's red-light district, the final sculpture has been banned from Belfast public land.

There's a labyrinth of medieval chambers hidden deep below a 15th-century pub.

The English Civil War began right here in 1642.

An engineering error ensured this cavernous 350-foot-long subterranean thoroughfare was never used as intended.

These quaint stepping stones traverse the river that connects three of England’s most beautiful lakes.

Engineering ingenuity during the battle of Gibraltar.

An 11th-century Viking gravestone in a Victorian parish church graveyard.

This museum contains a vast array of puppets and marionettes from all over the world, featuring incredible works by Portuguese creators.

This little-known national museum houses over 40,000 works of art from across the world.

This historic cemetery is home to the largest private mausoleum in Europe.

A museum dedicated to one of Portugal's most celebrated writers.

Little-known artist couple chose a former silk factory as the location for a museum dedicated to their work and other avant-garde art.

In addition to showing films, this one-screen arthouse cinema from the late 1940s is a museum of old film equipment.

Tucked away inside this concrete building is a church and its grand display of brutalist architecture.