An atmospheric, medieval-themed book store hides in a 13th-century underground space.

A medieval church built into an ancient cave.

This stone quarry was used to make axes and other tools more than 6,000 years ago.

Journey through the ruins of this ancient Roman temple dedicated to the god of war.

The ruins stand as a somber reminder of France’s worst civil catastrophe of the 20th century.

Half a century after it was abandoned, this ghost town is coming back to life.

Inside this museum, Christians were imprisoned when the Romans controlled Gaul.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

Estonia's largest creative city is a vibrant bohemian hub located within a former industrial complex.

The church's remarkable frescoes incorporate Finnish artist Hugh Simberg's trademark themes of death and the supernatural.

Man-made mineral caves house massive bat colony.

This intricately spiralling forest was created as a monumental work of art.

A trio of giant wooden megaphones turn up nature's volume in this Estonian forest.

This honeycomb-textured tafone looks like a petrified troll head.

Once standing on solid ground, this slender beacon is a victim of the very shoreline it was charged with announcing.

The secret cells in the basement of the KGB's Estonian "Grey House" have been preserved as a grim Cold War museum.

The labyrinthine home of the National Archives of Estonia is an experimental blend of architecture, art, and history.

Two old windmills got a new life as oversized sculptures of a man and a woman.

A replica of the home of a famous fictional troll family.

This old Estonian mine has been kept like a sprawling time capsule of the local shale industry.

Wars fought and wars won are remembered by these abandoned bunker ruins.

Hundreds of unusual wheel crosses poke above the earth in this small Estonian cemetery.

The gutted remains of this Estonian mansion are a monument to a tragic love.

This abandoned fighter jet launch center is now a haunting street racing course.