"Only the dead get off at Kymlinge."

Stockholm's deepest subway station is also a stunning ecological wonder.

A golden plaque marks the site of the mysterious unsolved assassination of the former Swedish prime minister.

Stockholm's narrowest alley is barely over two feet wide.

The discovery of an old wall led to the creation of this fascinating museum about the city in the Middle Ages.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

It houses the remains of a 17th-century version of the Titanic.

A gigantic collection of teeny, tiny books.

This mysterious but iconic tapered tower appears in many Azeri fairytales and legends.

Mysterious hillside with a continuously burning natural fire.

Home to nearly a third of the world's mud volcanoes, Azerbaijan is home to a messy, bubbling, and sometimes explosive landscape.

Resonant stone, that has been played since prehistoric times.

A former imperial sea-fortress and Soviet prison.

This Estonian watchtower looks like a big tree with two giant bird nests on it, complete with a "golden egg."

This behemoth bovine guards an Estonian town and is a memorial to the lost species.

This stoic bronze soldier stands as a symbol of Russian sacrifice or Soviet oppression, or maybe both.

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

Historic slum of Tartu.

A wooden replica of France's famous tower.

This dizzying tower was built to better broadcast the 1980 Moscow Olympics.

The Guardian of Tallinn.

Abandoned Soviet base once stocked with short and medium range missiles pointed at western Europe.

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

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