The Baden thermal baths are the oldest known hot springs in Switzerland. They are located in Baden and neighboring Ennetbaden in the canton of Aargau, on both sides of a prominent bend in the Limmat river. At the intersection between the Swiss Plateau and the Folded Jura, the thermal water flows through layers of shell limestone and rises to the surface in the spring area through fissures in the Keuper layer above. Of the total of 21 springs, 18 are located in Baden and three in Ennetbaden. The water has an average temperature of 46.6 °C and contains a particularly high proportion of calcium and sulphates. With a total mineralization of 4450 mg/l, it is the richest in minerals in the entire country.
The Celts were the first to use the healing powers of thermal water during the late Latène period. At the beginning of the 1st century, the Romans built important thermal baths, in the immediate vicinity of which the small town settlement of Aquae Helveticae was established. It is possible that bathing continued uninterrupted in late antiquity and the early Middle Ages. There have been written sources about the baths since the 13th century. During Habsburg rule and after the conquest of Aargau by the Swiss Confederates, Baden was one of the most important spas in Europe and was visited by numerous high-ranking individuals. It was not least because of the baths that the Confederates held their most important conventions here from 1416.
The attraction began to wane from around 1500 and reached its first low point towards the end of the 18th century. In the 19th century, Baden's baths once again experienced a heyday when spa treatments became a mass phenomenon. Massive investment in hotels and bathing facilities increased their appeal and attracted a wealthy international clientele during the Belle Époque. The decline began during the First World War and accelerated from the 1950s onwards. Baden missed out on modern developments and around the year 2000 the spa business almost came to a complete standstill.
The historic spa district is dominated by 19th and early 20th century spa architecture characterized by classicism and historicism, while only traces of the Gothic and Baroque buildings of the late Middle Ages and early modern period remain. At the beginning of the 21st century, the area was in need of redevelopment. New impetus was provided by a revitalization project that was opened in November 2021 and includes a new spa designed by architect Mario Botta. At the same time, publicly accessible bathing fountains were inaugurated in Baden and Ennetbaden.SRF from November 19, 1921: Thermal bathing for all - it started with a guerrilla action
Location
The bathing quarter, as the area around the thermal springs is known, lies on both sides of the Limmat at an altitude of around 360 meters above sea level, with the town of Baden on the left bank and the municipality of Ennetbaden on the right (Ennetbaden belonged to Baden until 1819). The fast-flowing Limmat, which is squeezed into a narrow riverbed, comes from the south. In the source area, it reaches the foot of the steeply rising “Goldwand”, which is partly planted with vines, where it changes direction and turns to the west.
The “ Great Baths” of Baden, the western part of the baths district, are located on a step in the terrain on the inside of the narrow bend in the river. The Mättelipark delimits the area to the west, while a batter on the south-western side forms a natural boundary to the Haselfeld, which is around 20 meters higher. The spa gardens with the Kursaal and the Baden Spa Theater are located there. The “ Little Baths” of Ennetbaden, the eastern part of the spa district, consist of a row of houses along the riverbank.
Two bridges cross the river. The inclined bridge, opened in 1874, has an incline of 7.5% to compensate for the nine-metre difference in height between the Baden bank and the lower-lying Ennetbaden bank.Mittler: Geschichte der Stadt Baden. Volume II, p. 189–192. The Mercier footbridge, named after the French bath masseur Henri Mercier, who was also a local historian, has been in existence since 1968.Heinz Meier: «Von hüben nach drüben». (PDF) In: Ennetbadener Post, No. 1/2005. Municipal Administration Ennetbaden, March 2005, pp. 13-15, archived from the original on May 1, 2016; retrieved on March 27, 2017.
Geology The thermal springs are among the best studied in Switzerland. To this day, it has not been completely clarified where the water seeps away and returns to the surface.Schaer: Stadtgeschichte Baden. p. 10. Baden and Ennetbaden lie at the intersection of the Swiss Mittelland and the Jura folds, which is reflected in the pronounced fold formation. The Lägern, a mountain range up to 866 m high, dominates the area and extends about ten kilometers eastward from the banks of the Limmat. Most of its rocks are from the Jurassic and Triassic periods. The latter is divided (from bottom to top) into layers of red sandstone, Muschelkalk and Keuper.Münzel: Die Thermen von Baden. p. 18–19. +Minerals of the thermal waterSchaer: Stadtgeschichte Baden. p. 11.Cationsmg/lAnionsmg/lAmmonium0.78Fluoride3.1Lithium4.8Chloride1185Sodium720Bromide2.5Potassium663Iodide0.009Magnesium99Nitrate< 0.5Calcium503Bicarbonate487Strontium6.2Sulphate1375Iron0.013Hydrogen phosphate0.05Manganese0.016Hydrogen arsenate0.1Copper< 0.005Molybdenum< 0.005Zinc< 0.01Lead0.002Aluminium0.018 In the spring area, the water-bearing shell limestone layer reaches 28 meters below the surface. It is overlain by impermeable Keuper and glacial gravel. Due to constant erosion by the Limmat and tectonic faults, the Keuper in this area is heavily fissured, so that the thermal water can escape despite the lack of shell limestone outcrops.Münzel: Die Thermen von Baden. p. 39–40. This occurs under high artesian pressure: on the Ennetbaden side, for example, the pressure level is ten meters above the water level of the Limmat.Geologischer Stadtführer. (PDF; 1,0 MB) City of Baden, 2004, archived from the original on May 1, 2016; retrieved March 27, 2017. The springs form an interconnected system based on the principle of communicating vessels: If one spring is regulated or a new outlet is created, this has an impact on the output of all the other springs. Changes to the spring intakes and interventions in the Keuper layer can have serious consequences, in the worst case scenario causing all the springs to dry up.
According to current knowledge, the thermal water of Baden is almost entirely precipitation water that has remained in the ground for varying lengths of time. Analyses of radioactive isotopes indicate four components. The largest portion is water that is more than 1000 years old and contains minerals from evaporite rocks of the Middle Triassic. It originates mainly from the Jura to the west and reaches the crystalline basement through eastward overthrust areas, where it rises again. It is possible that some of this crystalline water comes from the Black Forest to the north. For this to be the case, it would have to flow beneath the poorly permeable Permo-Carboniferous trough of northern Switzerland. There is also valley groundwater a few years old with a lower mineral content, fissure groundwater from the shell limestone layers of the Müseren plateau on the western edge of the city, and a small amount of deep groundwater from granite layers several kilometers deep.Werner Kanz: Die Badener Thermalquellen – neue Erkenntnisse zur Frage ihres Ursprungs. In: Badener Neujahrsblätter. Volume 80. here+now, Baden 2005, , pp. 122-128 (e-periodica.ch).
Characteristics of the thermal water On average, the amount of thermal water escaping is about 700 l/min, or about one million liters per day. Occasional fluctuations between 600 and 900 l/min may occur, but extreme values of 540 and 980 l/min have also been measured.Die Thermen von Baden. p. 65. The amount of effusion is related to the amount of precipitation, with an interval of about ten to eleven months. The amount of spring water shows less pronounced fluctuations than the amount of precipitation. Individual months with low and high rainfall therefore have less impact than longer periods of dry and wet weather.Die Thermen von Baden. p. 71. The clear thermal water has a noticeable odor of hydrogen sulfide, although the intensity of the odor can vary depending on the source or pipe. The taste, on the other hand, is not particularly characteristic.Die Thermen von Baden. p. 83–85.
The thermal water is characterized by a high total mineralization of 4450 mg/l and is considered the richest in minerals in Switzerland.Thermen und Quellen. City of Baden, 2016, accessed May 20, 2017. Erna Lang-Jonsdottir: So schneiden die Aargauer Thermalbäder im grossen az-Test ab. Aargauer Zeitung (online), December 29, 2011, accessed May 20, 2017. The calcium and sulfate content is particularly high. The high calcium content and the salt deposits resulting from the oxidation of the spring gases cause significant sinter deposits in the area of the springs and in all the installations that come into contact with the water. The average temperature of the water is 46.6°C, with variations between 45 and 49°C depending on the source. The water is slightly acidic, with a pH of 6.43.Schaer: Stadtgeschichte Baden. p. 10–11. It has a positive general effect on the whole organism, especially on the autonomic nervous system. Bath cures are particularly suitable for rheumatic complaints, mechanical damage, certain neurological diseases and metabolic disorders.Die Thermen von Baden. p. 274.
There are 18 springs, two of which are in Ennetbaden. Two springs in Baden and one in Ennetbaden are not used. All 21 springs are located in an area on both sides of the Limmat River that stretches 180 meters from west to east and 50 meters from north to south.Münzel: Die Thermen von Baden. p. 39. The most productive spring is the Grosse Heisse Stein in the middle of the main square of the bathing quarter, named after a huge slab of stone that covers the mouth of the spring. The Limmat spring, which once flowed into the river, is tapped directly from the riverbank. In the Middle Ages, the St. Verena spring was considered particularly beneficial for infertility, which is why it is named after St. Verena, the patron saint of conjugal love. A special feature is the cold spring in the Limmathof dependency, which is no longer used: although its water is identical in composition to that of the other springs, it is significantly cooler, at 21.5°C.Münzel: Die Thermen von Baden. p. 48–58.
Architecture of the baths district
The Baden part of the bathing quarter is geographically isolated from the rest of the city due to its location on the inner side of the Limmat knee and below an embankment. The buildings grouped around the Kurplatz, the Bäderstrasse and the Limmatpromenade are densely packed and partly interlocked. While only traces of the Gothic and Baroque buildings of the late Middle Ages and early modern period remain, the Classicist and Historicist spa architecture of the 19th century predominates. There are architectural references to Ennetbaden on the opposite bank of the river.
Kurplatz