Hang Toi, more commonly known as Dark Cave, has been tweaked to appeal to adventure seekers. Despite all the added artificial frills such as arriving to the entrance via Vietnam’s longest zip-line, the main attraction is venturing into the cave with just headtorches and plunging into a narrow cavern full of thick, wonderfully gloppy, gooey mud. “Dark” may refer to the unlit cave itself or your body after the mud bath. Either way, prepare to get dirty and have some primitive fun.