Đáy River
The Day River () is a river in Vietnam. It was formerly known as Hát River ( or ) or Gián Khẩu River (). The river is a distributary of the Red River, draining into the Gulf of Tonkin. The river has a length of 240 km and has a drainage basin of more than 7,500 km, flowing through Hanoi, and the provinces of Hòa Bình, Hà Nam, Ninh Bình and Nam Định.