Ngọc Sơn Temple and the lake turtle

In front of you, the red Thê Húc Bridge leads to Ngọc Sơn Temple, the "Jade Mountain". In a hall at the back is something that blends myth and biology: the body of a giant turtle from the lake.

1The real turtles

For centuries enormous soft-shelled turtles were seen in Hoàn Kiếm Lake, and people linked them to the turtle of the Lê Lợi legend. One died in 1967; its body, about 250 kilos and over two metres long, is preserved in the temple. In 2011 the last turtle, which was sick, was hauled out of the lake before huge crowds to be treated: it weighed 169 kilos. It died in January 2016, and its death shook the city.

To scientists it was a turtle of an extremely rare species; to many locals it was "Cụ Rùa", the "venerable great-grandfather turtle".

2A species of its own?

The biologist Hà Đình Đức described it as a new species, Rafetus leloii, in honour of the emperor. Most specialists, backed by a genetic study published in 2013, consider it the same species as the Yangtze giant softshell turtle, Rafetus swinhoei, of which only a handful of individuals remain in the world.

The bridge was built in 1865 on the initiative of the scholar Nguyễn Văn Siêu, who also raised the Pen Tower. Three words are carved on it: "write on the blue sky".

3What to look for

• Thê Húc Bridge, "where the morning light rests".
• The Pen Tower, a stone column topped like a writing brush.
• The greenish water of the lake, where the turtles once lived.