Laos is a popular tourist destination known for its beautiful scenery and ornate temples , however not many people venture below the surface and discover that what is underground is perhaps even more spectacular . The wondrous Tham Khoun Ex caves are so exquisite they do n't look real at first , which is perhaps why locals believe that spirits inhabit the underground wonderland . Cave photographer , John Spies , 59 , captured the sheer magnificence of the vast , yet intricate , underground wonderland . Enormous banks of terraced flowstone decorate the walls of the cave in many places . This slowly growing mound of white and orange calcite is one of the larger deposits along the river passage . Rippling reflections : A blue-tinted glow from outside illuminates the entrance chamber of the cave . Not your usual day out ! Floating on clear deep water and reflections near the cave entrance , visitors can either bring their own kayaks or rent boats from the local community to paddle deep inside the cave and marvel at its wonders . Tham Khoun Ex caves , commonly known as Xe Bang Fai River caves , feature imposing stalagmitemade of mineral deposits . With over 15km ( nine miles ) of awe-inspiring passages and wide expanses of water , it really is one of Laos ' hidden treasures . There is even a vibrant forest thriving at the upstream entrance to the caves , the lush green colour contrasting with the enormous white and orange banks of terraces flowstone that decorates the walls . Visitors are able to kayak through the waters , or explore adjacent chambers on foot . The cave is only able to be safely accessed during the dry season from November to April and during this time the water is clear and deep with a rich green hue . For some of the grander shots , a team of four equipped with powerful LED lights and walkie-talkies helped to light-paint this enormous cavern for this long exposure shot . In 2008 , an expedition , co-led by veteran caver John Pollack lead to the mysterious caves being mapped and photographed for the first time . What the explorers discovered about the little-known cavern was a vast river cave , which means a cavern with an active water source flowing through it . 'Everything about the cave is big-from its towering entrances to its phobia-inducing spiders , which can be 10inches across , ' Pollack told National Geographic . Nature at its best ! The upstream inflow entrance of Tham Khoun Xe has a verdant forest inside a huge collapsed doline . It is possible to kayak from the resurgence to here and back in one full day . Hidden secrets ! Massive formations abound in a newly discovered fossil section of the cave , 50 metres above the river level . This section , encrusted with delicate formations and not yet open to tourists , is one of several higher passages that lead to jungle shrouded entrances on . Gigantic ! The Giant Gour in the Oxbow area of the cave is 60 metres long and is probably one of the worldís largest rimstone basins . American cave explorer Dave Pierce marvels at giant cave pearls which grow like pearls in an oyster with concentric layers of calcite slowly building up year after year . Lit up ! The subterranean passage of the river is spectacularly decorated with calcified formations . Heading into darkness , a visitor paddles a small canoe near the downstream entrance . In the dry season from November to April , the only part of the year safe to visit the cave , the water is clear and deep with a rich green hue . This gigantic section , is also not yet open to tourists , is one of several higher passages that lead to jungle shrouded entrances . The Giant Gour in the Oxbow area of the cave is 196 feet long and is probably one of the world 's largest rimstone basins . The pool is filled with water during the wet season . The rims of basins like this grow taller each year as calcite precipitates from cave water as it flows faster over protrusions . The immense proportions of Tham Khuon Xe , one of the worldís greatest river caves , are difficult to photograph . A team of four equipped with powerful LED lights and walkie-talkies managed to light-paint this enormous section for this long exposure shot . Suphaporn Singnakphum stands amongst lush low-light plants in an underground garden in a huge fossil passage that adjoins the inflow entrance of Tham Khuon Xe . Water painting with kayaks and submerged LED lights near the downstream entrance of the cave . Visitors to Tham Khuon Xe can rent canoes or kayaks and paddle upstream to view the stunning calcifications on the cave walls . Sunlight streams into the mist-filled fossil passage near the sink of the Xe Bang Fai River . This section supports a verdant garden of ferns and other low light plants . Water painting with kayaks and submerged LED lights near the downstream entrance of the cave . A cave explorer amongst giant stalagmites in the Stairway to Heaven area of the cave . The cave is formed by the Xe Bang Fai river , a major tributary of the Mekong .
National Geographic cave has 15km of spectacular caves waiting to be explore by kayak . Explorers can witness the incredible caverns , lake and even the vibrant forest at the entrance . Cave photographer John Spies captured the labyrinthine chambers to unfold the mystery .