Hoàn Kiếm Lake, Hanoi (must see)

Hoàn Kiếm Lake (Vietnamese: Hồ Hoàn Kiếm, Hán tự, meaning "Lake of the Returned Sword"), otherwise known as Sword Lake (Hồ Gươm) or Tả Vọng Lake (Hồ Tả Vọng), is a fresh water basin in the historical center of Hanoi. This 12-hectare body of water is one of the major scenic spots in the city and a focal point for its public life.

In the past, the lake was variously named Hồ Lục Thủy (Vietnamese for "Green Water Lake", aptly named for its water's color) or Hồ Thủy Quân ("Mariner's Lake").

According to legend, after defeating the Ming China, Emperor Lê Lợi was boating on the lake when a Golden Turtle God (Kim Qui) surfaced and asked for his magic sword, Heaven's Will. Lợi concluded that Kim Qui had come to reclaim the sword that its master, a local God, the Dragon King (Long Vương), had given Lợi sometime earlier to defeat Ming China. Later, the Emperor gave the sword back to the turtle after he finished fighting off the Chinese. Emperor Lợi renamed the lake to commemorate this event.

The Turtle Tower (Tháp Rùa) standing on a small island near the center of the lake is associated with this legend. Large soft-shell turtle species, named Rafetus leloi in honor of the emperor, have been sighted in the lake for many years. The last known specimen here was found dead on January 19, 2016. There are three more remaining representatives of this species still at large.

Near the northern shore of the lake lies the Jade Islet, upon which stands the Temple of the Jade Mountain (Ngoc Son). The temple was erected in the 18th century to honor several prominent individuals, including 13th-century military leader Tran Hung Dao who distinguished himself in defeating the Mongol invasions of Vietnam thrice; the classical scholar Van Xuong; and Nguyen Van Sieu, a famous writer and official who undertook repairs of the temple in 1864. It is owing to that renovation that the temple got its current appearance, including Tran Ba communal house, the vermillion-red Thê Húc Bridge ("Perch of the Morning Sunlight") that links Jade Islet to the shore, and the Pen Tower.

The latter, one of the key tourist sights in Hanoi, stands 12 meters in diameter and 4 meters high, and has five floors. In the body of the tower, Nguyen Sieu carved three words “Ta Thien Thanh”, meaning “Writing to the blue sky”. The tower features Thien-Nhan architectural style and symbolizes harmony between natural and man-made worlds.