Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

In the foothills of the lesser Caucasus, a centuries-old fortress still stands.

After visiting hours, this picturesque waterfall is essentially turned "off" to be used for hydroelectric power.

This Armenian monastery was carved out of cliffs and named after the spear used to stab Jesus.

An underexplored, 130-foot tropical waterfall that you will have all to yourself.

Malaysian fireflies create a dazzling display as thousands light up in unison.

These termites have an large and deadly abode—impressive by day, dazzling by night.

Queen of the waterlilies, so big and strong it can support the weight of a human.

You feel like you're in a forest, but you're actually walking amidst the branches and trunks of a single giant tree.

World's largest open air theater spans 24 acres and hosts a massive recreation of the Passion of Christ.

The haunting peak of an old church is all that remains of a drowned Brazilian city.

Site full of incredible prehistoric paintings and archeological findings.

A series of haunting wooden totems are hidden in the woods surrounding a German environmental center.

A Serbian church lit by chandeliers made of weapons.

After mysteriously refusing to surrender at the end of World War II this sunken submarine was only salvaged in a search for Nazi gold.

17th century puritan church with connections to the Salem Witch Trials.

The quiet field that inspired one of the most famous songs of all time.

A Red Cross memorial museum at the site of the Niš concentration camp that operated for four eventful years during World War II.

Structure built from the skulls of vanquished foes.

This memorial park stands on the site of one of the largest mass executions of the Second World War.

A historical puzzle lies at the origins of this structure.

A spectacular Bulgarian cave resembling a devil's head with a waterfall rushing down its throat.

UNESCO-protected ancient burial ground.

Ruins of an early Roman Christian church dating back to the 4th to 5th centuries.