Nguom Ngao Grotto, a word in the language of Tay ethnic group, means "a cave in the middle of a stone valley". It was discovered by the local residents in 1921 and was a large cave established from the weathering of limestone for a long time. The cave stayed far from Ban Gioc Fall about 3 kilometres, belonging to Gun Hamlet, Dam Thuy Ward, Trung Khanh District. The entire system of the grotto has the length of 2,144 metres, containing three main gates: Nguom Ngao, Nguom Lom (or Nguom Luong) and Ban Thuon. The two gates Nguom Luong and Nguom Ngao have been used for tourism purpose - serving the excursionists' demands. Currently, only about 1 kilometre (800 metres) of the grotto has been discovered to be used by tourists.

Under the light of five primary colours, the grotto still keeps its primitive, wild and mysterious features. The Creator has cleverly created attracting stone statues with different shapes. Some of the statues' shapes look like human beings; some are similar to wild plants or animals in the legendary stories. Especially, in the cave, there are very beautiful spots inside like a room with statues of a fairy combing her hair, an indulgent saint, a gigantic lotus bud, a pillar supporting the firmament, etc. The stalactites grow from the ground or lowering from the wall. They lie in both vertical and horizontal lines, knitting with each other so that it makes up an occult beauty attracting lots of travelers.

	The stone with the shape of a lotus bud turning up side down

With a primitive and fascinating beauty carrying strong characteristics of Viet Bac region, this grotto has been recognised as a national beauty spot by the Ministry of Culture and Information and has brought a large amount of excursionists from inside and outside the province.