One of the oldest structures in Helsinki is this burrow grave that dates back to the Bronze Age.

The birthplace of the Japanese idiom "wet clothes" meaning “false accusation."

The center of this Polish border town was so thoroughly wiped out in World War II that only the foundations remain.

This formerly-prosperous Silesian mining town was completely demolished in the late 1960s and early 1970s as an attempt to cover up a secret Soviet uranium mine.

The final resting place of this rock icon has become a pilgrimage site for AC/DC fans.

This massive sycamore tree has been labeled as one of the largest in the state.

In the bowels of a 19th-century brewery lurks a fine-dining restaurant offering an array of themed feasts.

Only known mainland rookery of the threatened Stellar sea lion.

A popular swimming hole that hides one of America's most deadly diving spots.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

The first and only carousel with a lineup entirely of insects.

Home to an endangered salamander, a full moon celebration, and a large spring-fed outdoor swimming pool.

A shrine in Karachi is home to around 100 crocodiles that are regarded as sacred.

The home and birthplace of Caroline Dormon, a naturalist, artist, and the "mother of the Kisatchie National Forest."

An eccentric German artist built this weird and wondrous castle packed with shocking sculptures and alien art.

A wonderland of caves in eastern Iowa.

The warmest cave in the Ozarks features two seemingly bottomless lakes.

A limestone grotto where daylight filters in from below and turns the water a beautiful turquoise. Also home to a small underwater nativity scene.

This lakeside bunker complex in Mamerki, Poland, housed the Supreme Military Command of Nazi Germany during World War II.

This lake sits on an estimated 4 million tons of salt.

The largest lake in the Faroe Islands seems to be held hundreds of feet above sea level thanks to an optical illusion.

The narrow passages will challenge even the bravest driver.

In a largely deserted ghost town, a little brick building recalls its history as a gold rush hub and haven for outlaws.

A must for film lovers in Madrid and home to the Spanish Film Library's projection space.