Malaysia's Gunung Mulu National Park that stretches over 130,000 acres, is home to beautiful rainforests, rivers and mountains. However, its biggest attraction is its spectacular never ending cave system, which is so large that 30 years and 186 miles later, explorers are nowhere close to the end.

The first expedition to the caves was undertaken by the Royal Geographical Society, 30 years ago. Since then, explorers have been returning every two years, for three week stretches to try and map the entire cave system with lasers and other equipment.

Among the areas identified so far, is the world's largest cave chamber - The Sarawak Chamber which at 2,300 ft. long, 1,300 ft. wide and about 230ft. high, is big enough to fit 40 Jumbo Jet planes and, is three times larger than the previous title holder - the Big Room in Carlsbad National Park, New Mexico. To get to it requires walking along a narrow ledge and swimming across a river.

Named after a river that runs through it, the 100km Clearwater cave is Southeast Asia's longest cave. Known for its gorgeous stalactites, stalagmites, and rock corals, the cave is prone to flash floods, making it a little dangerous for visitors.

Deer Cave, the largest cave passage known to man, is believed to be big enough to fit London's highest point, the St. Paul Cathedral - five times over! However, its main attraction is the millions of wrinkle-lipped and horseshoe bats that live at the West End of the cave.

With new caves being discovered constantly, expedition members believe that there is so much left to be explored that it will take a few generations to find them all!

Sources:lonelyplanet.com, fwix.com,dailymail.co.uk.wikipedia.org,