Incredible places: A window onto extraordinary landscapes on Earth

Kawah Ijen is an active volcano on the island of Java with an extremely acidic crater lake and gas emissions that produce blue flames upon contact with oxygen in Earth's atmosphere.

The Denmark Strait cataract is a sloping portion of the seafloor between Iceland and Greenland that funnels cold water from the Nordic Seas into the Irminger Sea, fueling Atlantic Ocean currents.

The Marble Caves sit on the shores of a turquoise glacial lake in southern Chile. Light bounces off the water onto the walls, creating a magical, ever-changing display inside the caverns.

The Fossil Forest in Dorset is a stretch of southern English coastline peppered with living mounds of limestone that hide the remains of cypress trees from the late Jurassic period.

The Hailin impact crater is a newly-discovered scar in the mountains of Northeast China left behind by a meteor impact, but geologists aren't sure exactly when this happened.

Argentina's El Ojo is said to harbor UFOs and the ghosts of ancient deities, but as far as scientists can tell, the island is simply a fluke of nature that formed through erosion and water currents.

Vietnam's Son Doong cave is so large, you could squeeze 15 Great Pyramids of Giza inside it and fly a Boeing 747 airplane through some of its passages.

Icebergs and other glacial fragments regularly wash up on Iceland's southern Diamond Beach, making the sandy strip look like a field of gemstones.

Carlsbad Caverns National Park in southeastern New Mexico is home to 119 known caves, including North America's largest cave chamber, the Big Room.

Scientists first described the flooded cave in 2016 but determined its extraordinary extent years later.