Thousands of onlookers cheered at Hoan Kiem Lake as the mammoth creature was pulled in after escaping capture last month.
It took 50 workers two hours to net the turtle and lure into a cage which was then transported by boat to a small island that was recently expanded and equipped with a small pond, known as the "turtle hospital," said Ha Dinh Duc, who has studied the creature for 20 years and considers himself its caretaker.
He said it will be kept on the island for medical treatment, but it's unclear how long it will take. Concerns mounted after the turtle was spotted with lesions on its head and shell, prompting the government to form committees and employ hundreds of workers to frantically clean debris and pollution from the lake.
The reptile is estimated to weigh about 440 pounds (200 kilograms) and is one of the world's most endangered freshwater turtles. There is one other turtle of the same species, known as Rafeteus swinhoei, in Vietnam and two others in a Chinese zoo. But its value to the nation has nothing to do with how rare it is.
Scientists say it is at least 80 years old, but many Vietnamese believe, as legend has it, that it is the same mythical creature said to have helped Vietnamese King Le Loi fend off the Chinese nearly six centuries ago.
After the victory, the king was said to be boating on the lake when a giant golden turtle rose to the surface and snatched the sword with its mouth before plunging deep into the water to return it to its divine owners.
Hoan Kiem Lake, which serves as the capital's centerpiece, translates as "Lake of the Returned Sword."