A 仙人洞 (Xianren Dong) is the home of the Xian, legendary Chinese immortals and enlightened people. As a result there are actually numerous Xianren Caves in China, most of them archaeological sites. The archaeological finds are interpreted as remnants of the mythical beings. The term has also a meaning in Taoism, which is sort of religious. So there are actually at least eight different meanings and translations:
仙人洞 actually means Cave of the Immortals, but it is often translated Fairy Cave, because as immortal and fantastic beings they resemble the general idea of fairies. However, it is actually unclear if those Xian existed. There is the chance they were an ancient (probably palaeolithic) civilization before the Chinese, which left strange remains and where thus elevated to a half-god status. We have a similar effect with megalithic remains in Europe.
However, we have the problem that there are virtually hundreds of Xianren Caves in China. It's a big country. As a result we have massive problems keeping them apart. In general, we try to separate them by the province where they are located, but in some provinces there are more than one, so we try to use the town instead.