This Neolithic passage tomb forms part of a World Heritage Site.

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

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

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

Local legend says the remains of Father Christmas lie within the medieval grounds.

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

A fantastic reconstruction of a 10th-century Viking longhouse.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

This beautiful, historic church looks like something out of a simpler past.

The oldest hall in Iceland was written of in the Sagas and features a centuries-old escape tunnel.

This hobbit-y little hot spring may be the oldest spring used by humans in all of Iceland.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

The remains of an entire Roman city can be explored in this interactive museum.

Hungarian self-built castle.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

This black sand beach was crafted from volcanic explosions including the historic Minoan eruption.

Every spring, locals see the shadowy figures of a ghost army of slain Greek soldiers descend upon this ruined fort.

This famous archeological mystery may be an ancient example of movable type.

This abandoned Greek island was the last active leper colony in Europe.

A Bronze age settlement on the Greek island of Santorini might have been the inspiration for Plato's Atlantis.