The Kochbrunnen (in German: boil fountain) in Wiesbaden is the most famous hot spring in city. It is a sodium chloride hot spring. Its name refers to the water temperature of about 66 °C.
The source on the Kochbrunnenplatz was first mentioned in 1366 as Bryeborn (Brühborn) and 1536 as Syedenborn (Siedeborn). The productivity is about 360 liters every minute. The fountain has well water when exiting a temperature of 66.1 °C, smells faintly of hydrogen sulfide and strong salty taste. It is clear, but turbid yellowish after 24 hours on air. The main flow is directed to the processing plant in the Kaiser-Friedrich-Bad. From there it passes into the extensive thermal water system of the city. It is used both for medicinal purposes (even in the hot springs in Aukammtal), as well as to heat the city hall.
To Kochbrunnenplatz and neighboring Kranzplatz hosts some of the Wiesbaden Grand Hotels: as the oldest hotel in Germany, which already in 1486 founded "Schwarzer Bock", the former "Palace Hotel" – it was the first ever with room phone – and the "Hotel Rose" which was launched in September 2004 now hosts the Hessische Staatskanzlei.