Vietnam is home to some of the most incredible caves in the world. The famous Hang Son Doong cave system is 40 stories at its tallest height, wide enough to accommodate a 747, and even has its own weather system. But anyone looking to explore the caves is going to have a 2-year wait ahead of them. Oxalis, the only company to currently offer trips to the caves, sold out of its 2017 dates within two hours. But having the chance to visit the 3-million-year-old caves is well worth the wait (and the $3,000 price tag). Giles Lever, the British ambassador to Vietnam, recently described exploring the caves as feeling like going to “another planet”.