Term for a large, ancient vessel, used in former times in the courtyards of Chinese temples and palaces, to store large volumes of water for use in case of a fire. This form of fire prevention was also introduced in the
Forbidden City in Beijing (fig.), which on 9 May 1421 AD, just a year after its completion in 1420, was struck by lightning, causing a fire that reduced three great ceremonial halls to ashes and even burnt the imperial throne to cinders, an event that had been predicted down to the day and hour by the keeper of the water clock. As a consequence, the emperor had him imprisoned with the warning that if the prediction did not come true, the emperor would have him executed. However, one hour before the event, the clock master swallowed poison and killed himself. Besides lightning, also the heating of buildings in winter was a fire hazard, as the rooms of certain palaces, such as at the
Beijing Summer Palace (fig.), were heated by burning wood in a special outlet adjacent of the building, that in summer could be closed off with a wooden panel, in order to prevent anyone from falling in. The Iron Sea is made from iron and large ones may weigh up to a thousand kilograms. The English name Iron Sea is a literal translation from the Chinese term tie hai (铁海) and hints that its water is inexhaustible, akin to that of the sea. Also been called Gate of the Sea.