In 1912, this idyllic Alaska landscape was blown apart in the largest volcanic eruption of the 20th century.

One of Alaska's most significant ancient sites, spanning millennia and cultures, is right under the feet of some famously fat bears.

The remains of a 13th-century stronghold built by the Welsh prince known as Llywelyn the Last.

Along the edge of this fountain are 365 smaller fountains that represent the days of the year.

This charming Latvian lane doubled as Baker Street on the Soviet Union’s version of Sherlock Holmes.

In the summer, the area around this sculpture transforms into a vibrant concert venue.

This 13th century Gothic brick castle is the largest in the world by surface area.

After the famous composer died in Paris, his sister snuck his heart out of the country to honor his wish that it be buried in their native country.

This 700-year-old structure is one of the most unique architectural and historic monuments in Gdańsk.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

Hidden in plain sight on the Hudson River is an abandoned train station where nature has taken over.

Rusting away on the edge of New Jersey are the remains of a Cold War missile launch site.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

The name Niarbyl means “the tail” and refers to the rocky formations that push out into the Irish Sea.

The “Coin Cabinet of Dresden” houses a collection of over 300,000 numismatic artifacts, one of the largest of its kind in Europe.

The largest model carrot in the world.

This sculpture marks the spot where one of the greatest Roman rulers was proclaimed emperor.

A whimsical cottage from the 1300s with a preserved Victorian-era post office inside.

Britain’s longest ancient monument, this great 8th century earthwork was built to mark the boundary between what would become England and Wales.

The first archaeological site discovered by aerial photography.

Twice a day this ancient path disappears with the tides, leaving the Holy Island of Lindisfarne out to sea.

One of England's most famous churches hides a pair of little known architectural treasures.

A labyrinthine underworld of tunnels and caverns hides beneath the city.