Google this keyword – world’s largest cave – and your first return not surprisingly will deliver a link to the world’s largest cave, Son Doong Cave. People have only known about this cave since 1991, and the wider world tuned in just a few years ago. It’s not easy to visit this cave yet, but it is easy to visit one of Son Doong’s sister caves such as Hang Nuoc Nut and Hang Va. And you can do this from Hue.