An abandoned saucer-shaped monument in the Bulgarian mountains.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

One of Australia's largest secondhand bookstores.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

Museum preserving torture methods from the past.

One of the world's steepest streets seems to have houses sliding down it.

Rippling sand dunes frozen in the Arizona rock.

A seemingly endless landscape of pure salt stretches far across Bolivia.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

The ancient water tanks remain some of the ruined city’s most beautiful architecture.

A rare pod of derelict midcentury Futuro and Venturo houses lines a semi-abandoned beachfront resort outside Taipei.

Over two-thirds of the world's population of giant tortoises live among this coral formation.

This deceptively salty lake looks like blushing pink lemonade.

Mined to a depth of 240 meters with a perimeter of about 1.6 km, the largest hand-dug excavation in the world.

This historic observatory was established to keep shipwrecks from littering the Cape of Good Hope.

Haven for Cape Fur Seals, until the Ring of Death of jumping Great White Sharks arrives.

On any given day this sprawling market houses literally tons of government-regulated gold, gems, and precious metals.

Whitewashed mosque contains the world's largest carpet.

One of the most remote lodges in the Amazon offers rare wildlife encounters and undisturbed views of the Peruvian rainforest.

On the outskirts of a desert trading village high on the Andean plain, steel giants have been destroyed by salt winds.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

A set of ancient drawings in the desert of Peru that are so massive, many of them can only be fully seen from the sky.

This stunning mass of ice spans 121 square miles and is still growing.