Bring your hiking shoes, wool socks, and thermal underwear for a stay in these cozy forest huts.

The world's first ice hotel is still one of the most elaborate and beautiful.

A series of modernist treehouse hotel rooms grace the outskirts of an Arctic forest.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

An illuminated manuscript comprising the life's work of a lone monk, inexplicably decorated with a portrait of Satan himself.

This World War II relic let Allied pilots know they were entering neutral airspace.

These moss-covered medieval ruins tower atop the smallest of Ireland's Aran Islands.

An oddly conical beacon perched atop beautiful Irish cliffs.

This beautiful site is where the first transatlantic telegraph was sent from.

Ancient Bronze Age rampart that was used into the middle ages.

The severed head of a 17th-century Irish martyr lies within an intricate golden shrine.

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

Impressive mining ruins overlook a spectacular view of Ireland's Copper Coast.

The ruins of a medieval monastery named after a type of tree.

This Bronze Age tomb is the centerpiece of a clearing within a beautiful Irish forest.

An ancient holy well said to be used by the patron saint of sailors and travelers, lost in the boggy west of Valentia Island.

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

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

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

This natural sea arch highlights Ireland's rugged coastal beauty.

This ancient Irish landscape boasts hundreds of legendary ruins.

These imposing walls and towers look more like the ruins of a fortress than a monastery.

A collection of housewares from recent Irish history adjoined by a tower from ancient Irish history.