When ecosystems collide in the arid Southwest.

Teeming with illegal goods and services, this towering maze of vice is also a popular tourist accommodation.

The last bastion of Roman presence north of the Alps looms over a German town.

This medieval castle overlooking the Elzbach river looks just like it did hundreds of years ago.

A rare cold-water geyser that bubbles to life every half hour.

A ruined castle stands atop a hill surrounded by dragon lore.

Twisted buildings adorn the banks of the Rhine river.

Southern Italy's spinning top village.

Between Neo-Pagans and Neo-Nazis, these strange rock formations have a curious cult following and a very strange history.

The last Tsar of Russia constructed this private church just so he could attend services when visiting his wife's hometown.

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

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

The world's oldest grape-producing vine has survived four centuries of turmoil and even has its own anthem.

This military tunnel dates back to World War II and provides visitors with a little wartime adrenaline.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

Bordered by forest on three sides and the ocean on the other, the Great Dune of Pilat is the highest sand dune in Europe.

Controversially restored in the 1970s, this giant 15th-century mosque is shrouded in legend.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This fort dates back to 1588 and was colonized by the Portuguese, Dutch, and English and sits prominently on the Indian Ocean where azure water lap the coast.

This Bogotá museum houses the world's largest collection of pre-Columbian gold relics.

This giant urban staircase was built to keep the city's brave fighting men from getting waylaid in the red light district.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

The largest 19th century panorama in the world still in-situ.