Top 5 amazing caves

Delve deep underground and explore some of the planet's hidden natural wonders

1. Hang Son Doong Cave

Location: Quang Binh Province, Vietnam

(Image credit: Dave Bunnell)

The world’s largest cave was only discovered in 1990 and first explored in 2009, but has been forming over the past 3 million years. It has been carved from limestone by the Rao Thuong River flowing beneath the Annamite Mountains and it is now so large that a 747 aircraft could fit within its biggest cavern. Inside are 80-metre-high stalagmites, cave pearls the size of baseballs, and even clouds formed as a result of the cave’s own localised weather system. Massive sinkholes have also opened up sections to the outside world, allowing jungle to take root inside.

2. Sistema Sac Actun Caves

Location: Mexico

The network of watery caves beneath Mexico’s Yucatan Peninsula contains the longest underground river in the world, measuring 312 kilometres. It is also the second longest cave system, behind Mammoth Cave in the US, but its true size was only discovered in 2007 when a group of divers found a passageway linking the Sac Actun and Nohoch Nah Chich cave systems together.

3. Mammoth Cave

Location: Kentucky, United States

With over 650 kilometres of surveyed caves and passageways, Mammoth Cave is the longest cave system on Earth. It is thought to have begun forming around 10 million years ago, when acidic rainwater started seeping through cracks in the area’s shale and  sandstone cap and into the limestone beneath. Over time the water dissolved the limestone rock, creating an enormous network of caves still being discovered today. Nearly every type of known cave formation has been found here, as well as over 130 species of flora and fauna.

4. Marble Caves

Location: Patagonia, Chile

On a peninsula of solid marble in the glacial General Carrera Lake is a series of swirling blue caves. Formed over the past 6,000 years by waves crashing against the rock, dissolving and then washing away the calcium carbonate, their colour is a result of the lake’s azure waters reflecting off the grey marble, meaning its intensity and hue changes depending on the water level and time of year. The lake is also home to Marble Cathedral and Marble Chapel, two small marble islands.

5. Vatnajökull Glacier Caves

Location: Vatnajökull, Iceland

Inside the Vatnajökull Glacier, the largest glacier in Europe, winds a series of spectacular ice caves. Some, such as the Kverkfjöll Caves, are formed when geothermal heat from hot springs beneath the glacier melts the ice, sculpting long, mesmerising open spaces that tunnel deep through the frozen water.


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