A little way inside the front gate are steps leading up to Tam Giac Pagoda, which is perched on a hillside and surrounded by trees and shrubs.

Tam Giac venerates the Sakya Mouni Buddha and the Chinese philosophers Confucius and Laozi, and there’s a big altar inside for the devout to do the same.

It’s from this point that Tam Thanh diverges from your run-of-the-mill Buddhist temple.

More steps lead down from the pagoda to the amazing Nhi Thanh Grotto, a deep cave whose discovery is officially credited to Ngo Thi Sy, the governor of Lang Son Province from 1777 to 1780, and a famous poet and scholar to boot.

At the mouth of the cave, a carved dragon and tiger look as if they are guarding the entrance. High up opposite the orifice is a statue of Ngo Thi Sy, which he ordered to be carved into the rock at the same time as the cave was enlarged.

To enter Nhi Thanh Grotto requires crossing a pool fed by a stream that flows through the cave and makes the air inside feel fresh and cool.

The main chamber turns and twists its way for half a kilometer past stalactites and stalagmites in abundance, and has many alleys leading off into pitch black darkness.

Concrete bridges and a well-hewn path make the going easy, and there is a large space half-way in that receives natural light from an opening high above.

Along the way, fish can be heard swimming in the stream and their tails seen flashing as the piscine troglodytes break the water’s surface.

Also inside the cave are stone steles inscribed with a score of writings by renowned thinkers of the past.