The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

Abandoned Coast Artillery fort now serves as graffiti canvas and sightseeing vantage point.

Underwater restaurant at the coral reefs of Eilat.

Cavernous opening completely encased in Karst limestone.

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

An underwater restaurant, surrounded by a coral reef.

This extraordinary geological oddity resembles human-made pavement.

Walk behind a 50-meter-high waterfall.

An island said to shake with the current.

Amazing pre-Civil War ruins alongside a shallow, rocky river that hosts beautiful (but endangered) lilies.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

Spirits from these lakes are said to produce the local weather and odd phenomena as they bicker between themselves.

A beautiful geyser under environmental threat.

Swarms of dainty flying insects swarm into the Petaloudes Valley to get busy.

This peculiar lake of pitch is so thick and viscous that one can walk on its surface.

Each year melting snow turns these Austrian hiking trails into scuba zones.

Spring that emits water and fire at the same time is said to have remedial properties, and sparked its own religion.

The red crab exhibits one of the most spectacular migrations on earth, despite manmade obstacles.

Submerged trees jut ghost-like out of an idyllic turquoise mountain lake.

The longest continuous lava tube in Oregon.

The true jewel of Africa's west coast known as "Africa's Last Eden."

Handcrafted thermal spa washes away each night with the tide.

Stone pillars and a petrified wedding party in the hills of North Macedonia.

The home of aviation trailblazers, in a remote corner of the big city.