Thang Long is the former name of the city of Hanoi, the capital and second-largest city of Vietnam. Located on the right bank of the Red River, present-day Hanoi is home to over 6.5 million people.
In 1010, Lý Thái Tổ, the first ruler of the Lý Dynasty, moved the capital of Đại Việt (大越, the Great Viet, then the name of Vietnam) to the site of the Đại La Citadel. Claiming to have seen a dragon ascending the Red River, he renamed it Thăng Long (昇龍, Ascending dragon) – a name still used poetically to this day.
Turtle Tower (Vietnamese: Tháp Rùa), also called Tortoise Tower is a small tower in the middle of Sword Lake in central Hanoi. The tower was erected on the Turtle islet, the former fishing site under king Le Thanh Tong. After the French conquered the Hanoi Citadel, most of the population around the lake fled away.
In 1802, when the Nguyễn Dynasty was established and then moved the capital down to Huế, the name of Thăng Long (昇龍, “ascending dragon”) was modified to become different Thăng Long (昇隆, to ascend and flourish). In 1831 the Nguyễn emperor Minh Mạng renamed it “Hà Nội” (河内, can be translated as Between Rivers or River Interior) .