Hoan Kiem Lake was once a section of the Red River which several thousand years ago ran through this area and later gradually changed its flow to the east, as seen today. In the past the Lake had the name Luc Thuy because its water was blue and clear all year round. In the 15th century, it was renamed Hoan Kiem (Restored sword) because it was related to the legend of King Le Thai To (Le Loi) returning the sword to the Tortoise Genie, marking the success of the 10 year-long struggle of Vietnamese people against the Ming aggressors (1417-1427) under Le Loi's leadership. The legend has it that during the insurrection in Lam Son (Thanh Hoa), Le Loi retrieved a sword from the lake and later picked up a hilt from a field. This precious sword accompanied him throughout the resistance war against the Ming invaders. Le Loi was crowned and set up the capital in Thang Long. One day while he was cruising on Luc Thuy Lake, a tortoise appeared. Just when he pulled the sword from it sheath, it flew into the tortoise's mouth and the animal immediately submerged, leaving the sword never to be seen again.

Since that day, Luc Thuy Lake was called Hoan Kiem(Restored Sword) or Guom (Sword) Lake. From the dynasty of King Le Trung Hung in the 16th century, the Le Kings and Trinh Lords began to embellish the lake. Before the French domination, the lake stretched to Hang Chuoi Street and later it was partly filled for the construction of villas. At present Hoan Kiem Lake has an area of 600 x 300m. It consists of the Tortoise Tower, Ngoc Son Temple, The Huc Bridge, Thuy Ta House, Hoa Phong Tower and trees growing on the lake's shore, creating poetic and attractive scene that fascinates many domestic and foreign visitors.