Though its name means “mysterious mountain”, Linh Son is actually a pair of limestone caverns named Heaven and Earth in Thai Nguyen Province, some 75 kilometers north of Hanoi.

Thien (Heaven) and Dia (Earth) can be found on the slope of Hot, a limestone peak in Linh Nham Commune, Dong Hy District. With a floor area of 360m² and hundreds of stalagmites and stalactites, Thien is a sight to behold and the locals reckon it in beauty like the much-vaunted Thien Cung (heavenly palace) in Halong Bay. Upon entering the cavern, you may feel lost in a fairy world amid all the fascinating beauty created by the variegated stalagmites and stalactites. They resemble many shapes, the most obvious being the two dragons, the kneeling elephants, dancing kylins and lions, and the prostrate tigers guarding the entrance. The floor is fairly level, which makes walking around very easy, and there are staircases cut into the rock leading up to hewn altars on which stand Buddha statues.

Just outside the other end is a road to the mountain’s summit and another to the even more impressive Dia. This cavern has a floor area of 480m² and higher ceilings than Thien. Again the going underfoot is level and easy, and there are plenty more stalactites and stalagmites taking on various familiar shapes, particularly a big pen brush and a mother embracing her child. It used to be a Buddhist temple of sorts and there are still a few bronze Buddhas, a number of red lacquered statues trimmed with gold, and many stone figures on man-made altars cut from the walls.

In October 1995, some local residents discovered an old stele on the cliff above the twin caverns with carved Chinese characters meaning “restoring Linh Son Cavern”. Archaeologists and Sinologists from the Museum Preservation Department checked it out the following year but they found that most of the carved characters had faded beyond translation. Going buy the design and decorations, they did manage to ascertain that the stele came from the days of the Le Dynasty.