An underground city of salt.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

This tiny island is home to the world's largest colony of Northern gannets.

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

This Birnam-based garden honors the legacy of 19th-century children’s book author Beatrix Potter.

Thanks to both terrific preservation and historic vandalism this ancient site is known as the "Heart of Neolithic Orkney."

This Scottish burial tomb once held hundreds of ancient eagle bones.

Enter the world under the hill at this ancient UK burial chamber.

Largest lake in Great Britain measured by surface area.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

A memorial to the beloved brown bear that served in the Polish army during World War II.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

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

A six-ton wedding present for the King of the Scots.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

A statue in the heart of Edinburgh honors a bear that served in the Polish military during World War II.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

This easily overlooked memorial immortalizes the scars from the 1956 Hungarian Revolution.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

Museum dedicated to the terror regimes of Hungary.

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

The modern birthplace of Irish freedom.