Ngoc Son Pagoda sits on an islet at the North end of the lake. The oldest structures in the complex dated back to 1225,though most of what you see was either built or reconstructed in the 19th century.
Ngoc Son Temple
In addition to the two beautifully ornate Confucianist sanctuaries dedicated to various long-dead humans, a huge stuffed turtle (which most certainly never swam in this lake) resides in a glass display case. The spot is lovely, not only for the ostentatious architecture, but for interesting people who take refuge from the city here. Your camera may capture old men playing checkers in the Pavilion of the Stelae, someone fishing quietly among the willows which practically obscure the island from view, a couple posing for their wedding photo with the Tortoise Pagoda in the background, or the young photographers who always gather on the red wooden bridge.
The water puppetry theater
Practically across the street from the bridge is the water puppetry theater. Scenes from Vietnamese lore and history (including ancient battles) are elaborately performed by colorful lacquered puppets in an indoor pond, accompanied by traditional Vietnamese folk music. It sounds awfully corny, but missing this Hanoi attraction is like going to Paris and skipping the Eiffel Tower. Tickets for the evening performances are cheap and sell out early in the day. Avoid seats closest to the water or you may get splashed.