It is a cavern in the main powerhouse of the underground power station on the left bank of the Three Gorges Dam and an important part of the power station design. With the construction of the Three Gorges Dam, No.484 hole was excavated accordingly. This hole is a water storage tank, which can be used to adjust the hydropower production and power grid load of the Three Gorges Power Station. Because the hole 3d484 is far away from the ground, special engineering methods such as high-altitude hoisting are needed in construction.