The Avenue of Mausolea is a series of grand palatial tombs.

Ethiopia's "smoking mountain" is in one of the hottest regions on the planet and is home to two lava lakes.

The hottest place on the planet.

Over the centuries, this island paradise has done it all, from providing monks with ecclesiastical respite to sheltering an exiled Leon Trotsky.

A fountain standing as a testament to a doomed alliance.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

A marvel of Byzantine engineering under the streets of Istanbul.

These gnarly desert trees produce the prized aromatic resin traded along the ancient incense trail.

Some claim these desert ruins are from the legendary "Atlantis of the Sands."

This bazaar is one of the oldest in the Arabian world.

This spectacular mosque houses the second-largest chandelier in the world.

A sinkhole and now a swimming hole, too, full of dazzling turquoise water.

Kenya’s oldest town is more than 700 years old and home to 6,000 donkeys.

Get tall with nature's lankiest beasts and their warthog friends at this Kenyan preserve.

An extensive audio-only collection of cultural heritage saved from a genocide.

Golden Gate Park's historic collection of plants.

This private residence was the template for one of the most beloved television homes of all time.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Dine on roast goat inside a scrapped 1960s Soviet airplane.

The world's largest frame offers spectacular views of the city's past and present.

This futuristic building is yet another architectural wonder in Dubai.

A preposterously luxurious hotel with gold-plated iPads, Rolls Royce chauffeurs, and a staff that trains by watching "Downton Abbey."

The oldest building in Hargeisa survived the 1988 bombings that destroyed some 90 percent of the city.