The world's largest man-made underground caverns offer unparalleled underwater wonders.

Rusted and decayed, this former mining site is a portal to the past.

A long-disputed island that Denmark and Canada claim by periodically alternating flags and bottles of liquor.

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

A granite plane marks the site where a French aviator completed the first airplane flight across the English channel.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

This skewed English house has looked like it's going to fall over for centuries.

An impressive armored bronze effigy marks the tomb of one of the medieval era's greatest warriors.

Inspired by Thomas Stothard's painting of the "Journey to Canterbury," albeit with Canterbury natives.

A defensive structure built during the Hundred Years War has remained useful in one way or another for nearly 700 years.

The bar where "The Great Train Robbery" was planned was once a nexus of high society and low morals.

The city that saw the birth of Sweden is now home to an impressive collection of work from its favorite artist.

This unique bridge is one of the last of its kind in Sweden.

The unique design of this former quarry provides ideal acoustics for concerts.

An oil drilling mistake created this fountain that has been spraying water for over 150 years.

Dine on food tied to Viking history and legend at this subterranean Stockholm spot.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

A 130-year-old urinal is the oldest of Stockholm and perhaps all of Sweden.

These pink granite water slides are the result of millions of years of erosion.

A subterranean haunt where wine and homemade biscottis are always on the menu.

Now nearly abandoned, Kaskaskia was once the capital of Illinois and one of the most important towns on the upper Mississippi.

The bomb-ravaged remains of of a colossal Neptune.

This former fascist summer camp was abandoned for decades.