Son Doong Cave

"Caves are fragile environments. They don't regenerate very quickly, and once they're broken, they're broken."
Unless you've been under a travel rock for the past couple of years, you've probably heard about the discovery of Hang Sơn Đoòng (HSD), the largest cave in the world. The good news? It's now open to explorers.
This post has been updated with additional context on other superlative cave systems. Sharing by john spies on 500px The