乾清门外两侧的10口大铀缸格外引人注目。大铜缸金光闪闪，在红色宫墙的映衬下，赤行富丽堂后皇，定做铜缸厂，气热血甚壮。然而，这些大铜缸和大铁昔日皇宫却不是装饿用品，而是用来贮水的防火用具。缸内平时注潢汪水，随时可以灭火。到了冬季，了了防止结冰，大铜缸大水缸，专有内务府太监负责在缸外套上校风套保温并加盖，缸底还要烯起炭火，直到来年春暖时才撤火。故宫博物院成立以后，重庆铜缸，为防止缸内积水，在缸底均钻有漏水孔。

The 10 large uranium tanks on both sides of the Qianqing gate are particularly striking. The big copper cylinder is glittering. Against the red palace wall, the empress of Chihang rich hall orders the copper cylinder factory, which is very strong in gas, heat and blood. However, these big copper tanks and big iron imperial palaces used to be fire-proof appliances used to store water instead of food. Water is usually injected into the cylinder to extinguish the fire at any time. In winter, to prevent freezing, the special eunuch of the Ministry of interior is responsible for the heat preservation and capping of the cylinder jacket, and the bottom of the cylinder needs to be filled with carbon until the next spring. After the establishment of the Palace Museum, Chongqing copper cylinder, in order to prevent water accumulation in the cylinder, all the bottom of the cylinder are drilled with water leakage holes.