Inside this Icelandic greenhouse, geothermal energy keeps tomatoes warm and growing.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

Three columns of volcanic rock shoot out of the ocean.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

Medicinal spa created with the discharge from a geothermal energy plant.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

Iceland's tribute to its thankless civil servants.

One of the oldest family businesses in Reykjavík serves lamb-based hot dogs.

This exclusive resort has completely covered a tiny Balkan island in a 5-star warren of guest rooms.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

Bridge that died in war and was resurected.

Quito's historic, main square dates back to the 16th century.

The last remnants of a massive medieval wall that once encompassed the city of Berlin.

Water and windows define this defensive Italian well.

Nine caves filled with recently-discovered archaeological finds under the houses and the streets of the most ancient district of an old town.

This picturesque Umbrian city has a subterranean side that has long remained hidden.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

The ancient latrines of the Greeks, in all their public glory.

A nightmare for the claustrophobic lies hidden in Southeast Asia.

The lavish temple of the Cao Dai religion that includes Buddha, Mohammed, Joan of Arc, and Victor Hugo.

A battle between nature and architecture in the Cambodian jungle.

5,000 skulls in memorial to those killed by the Khmer Rouge.