A nightmare for the claustrophobic lies hidden in Southeast Asia.

This French colonial post office is arguably the grandest in all of Southeast Asia.

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

This 135-year-old weather station studied the effects of the climate on human health.

A number of craters left by fatal mortar strikes have been filled with red resin to remember those lost during the Siege of Sarajevo.

An ancient theatre in the "little Rome of the Alps."

Ha Long Bay's "Cave of Surprises" houses a popular phallic rock formation.

Once thought to be the Garden of Eden it holds a holy footprint claimed to belong to Adam, Buddha and Shiva.

Known as the most scenic route in Sri Lanka, this train line is steeped in history and offers an unparalleled view of the country.

Ancient cave temple near a massive Buddha statue.

This ancient cave temple complex is the largest and best-preserved temple complex in Sri Lanka.

An ancient stone fortress considered by many to be the eighth wonder of the world.

This site was once the religious, cultural, and trade center of Sri Lanka.

A spectacular rainbow of stained glass makes the "Pink Mosque" one of the most beautiful in Iran.

A dreamy mausoleum honors Persia's most famous poet.

Named after a legendary garden called Eram in southern Arabia, built by order of Shaddad, an Arab king who wanted to compete with Paradise.

The ancient necropolis houses the immense rock-cut tombs of four Persian kings.

This ancient burial site is believed to be one of the first earthquake-protected structures in the world.

Long before air conditioning, Persian architects found an ingenious way to cool off.

The fire inside this temple has burned for more than 1,500 years.

Putrefaction plateaus in Iran, where the dead were sent for decontamination before going to their final resting place.

Ancient structures used to make and preserve ice in the deserts of Persia.

17th century mosque for Shah Abbas' harem.

This 17th-century structure is a beautiful testimony to traditional Persian architecture