The Hot Springs to Visit in the Hautes-Alpes, France
- Nature Source Chaude
- Published on
- Updated on 16 May 2025
Nestled between the Queyras Regional Nature Park and the Ecrins National Park, two hot springs have decided to make a steamy appearance on a plain dominated by imposing mountain ranges.
We are at the Plan de Phazy, a magical spot on the banks of the Durance where two hot springs, the Source des Suisses (Swiss Spring) and the Source de la Rotonde (Rotunda Spring), gush forth.
The water gushes from the rock, feeding four pools with temperatures ranging from 26 to 28 degrees.You can take a dip here all year round. The spring is overlooked by a building called ‘La Rotonde‘, after which it is named. Let’s take a closer look at this exceptional site before moving on to another equally remarkable site just two kilometres away. On the opposite bank of the Durance is a third hot spring. Another magical site, it is home to the petrifying fountain of Réotier.
IN SUMMARY:
Map of hot springs in the Hautes-Alpes
The N94 national road passes close to Le Plan de Phazy. In winter, the small road leading to the car park is usually quickly cleared of snow. Access to the baths is free all year round.
On the map:
– The hot springs of Plan de Phazy ;
– The petrifying fountain of Réotier ;
– The hot springs of Monétier-les-Bains.
Warning:
Soaking in the Plan de Phazy hot springs is normally forbidden. A decree issued by the Mayor of Risoul in August 2020 was posted on a metal post behind the upper pools at the end of June 2024.
See the map for more information.
Le Plan de Phazy: a past steeped in mystery
The hot springs at Plan de Phazy were certainly known to the Romans in ancient times, although few traces of their presence remain.
However, the remains of a Roman road can be found nearby: the Alpine Route. This followed the Durance up the valley to Briançon and then over the Montgenèvre Pass to Italy.
When the Romans entered the region and conquered Gaul, the hot springs of the Plan de Phazy were obviously a great promise of well-being.. All the more so as they were great lovers of thermal baths, a pastime they had turned into a veritable art of living.
Would Roman baths have existed at that time, even in a rudimentary form? It’s hard to say! For a long time after that, history was marked by plundering, destruction and abandonment. The spa buildings and facilities were among them. Many springs were devastated and some thermal stations were burnt down.
In the Middle Ages, three hospitals were built a few kilometres from the Plan de Phazy. One was in Saint-Clément, the other two at the foot of Mont-Dauphin and on its plateau. What was the purpose of these hospitals? At the time, military were accommodated in civilian hospitals or in private homes. The reputation of the thermal waters for the treatment of wounded soldiers was well known. What’s more, the Plan de Phazy and its surroundings were strategically located at the junction of three valleys, which explains the military presence there.
At the end of the 17th century, Vauban fortified the place of Mont-Dauphin, reinforcing his military presence and blocking access to the valleys for foreign powers. Tens of thousands of soldiers transited through the valley.
The Plan de Phazy hot springs were frequented by these soldiers as well as by the nearby garrisons (Mont-Dauphin, Embrun, etc.), who, together with the local population, made up the majority of spa guests.
In fact, it was the military stationed at Mont-Dauphin who were the first to study the properties of these waters. It was only later, in the 19th century, with the advent of the first instruments, that chemical analyses were carried out by scientists.
The Rotunda and its hot spring
The revolutionary period and the Napoleonic Wars (1803-1815) put an abrupt end to a certain enthusiasm in France for spa projects (new buildings, renovations, refurbishments). When they ended, a new page was turned. We are at the dawn of the modern age. The world was making great strides towards something different. Ambitious spa projects (Bourbonne, Vichy, Plombières, etc.) to more modest ones, in line with a new period of prosperity, came into being.
In 1824, during the reign of Charles X and Louis XVIII, a small bathhouse was built around the spring. This building was called ‘La Rotonde‘.
The image of a multi-purpose building combining accommodation and entertainment, common in spa towns at the time (1800-1850), is far from the reality here.
In fact, spa visitors already lived on the spot. They were mainly local people and military stationed at nearby garrisons (Mont-Dauphin, Briançon).
The Rotunda was built at the foot of the Barbein rock, on a platform of hardened tuff. It was built in the shape of an amphitheatre, backing onto the mineral spring. All around, a staircase gave access to the baths (six or seven) dug out of the rock.
This very simple type of construction meant that the mineral spring could be used directly from the rock, which limited the loss of the water’s properties and active ingredients. The medical use of mineral springs was as simple as possible: a bath in its raw state.
In 1935, an earthquake hit the Rotunda hard. The spring began to dry up and was then found a few metres outside the building. It was then once again able to join forces with the sun and fertilise the soil. To find out more about this, I invite you to read the article entitled: The soil, base layer and living medium of a hot spring.
The spring will escape any other spa centre project until now, which is a rather rare situation.
Presentation of the Plan de Phazy site
The Plan de Phazy site, which belongs to the communes of Guillestre and Risoul, is situated at an altitude of 900 metres and has two hot springs.
The first is near the road that leads to the Rotunda spring. It is not very interesting. The water is lukewarm (26 degrees Celsius) and not ideal for bathing, unlike the neighbouring Rotunda spring, which is 27-28 degrees Celsius. At this temperature, every degree counts.
This spring, known as either the ‘Source des Suisses‘ or the ‘Source des Vignes‘, provides the water used to heat the horticultural greenhouses.
Despite a flow rate of 300 litres per minute, the area around the capture point often leaves only a few traces of iron deposits in a field, which are visible from the small road depending on the surrounding vegetation.
The second hot spring is the Rotunda Spring. The water gushes out of a pink marble rock at 28°C (the water in the first pool is 27.4°C), just a few metres from the building. This is where the spring water mysteriously reappeared after the earthquake.
You can also see thermal plankton on the fountain. It looks like green foam and can also be seen in the four circular pools. The spring flows at a rate of 70 litres per minute.
The water that flows through the four pools eventually trickles down to an orange-coloured plateau of ferruginous tuff.
The chemical elements dissolved in the water encourage an exceptional biodiversity characteristic of salt meadows. In fact, the Plan de Phazy site has been classified as a Natura 2000 site. This protected area is home to the only salt meadow in the Provence-Alpes-Côte d’Azur region.
The rotunda spring: the nature of the water and its therapeutic properties
There is a common chemical typology used to classify thermal waters. They are sodium chloride waters.
This name comes from the fact that the main anions (negative ions) in this water are chloride ions. The main cations (positive ions) are sodium ions. Other major elements are also present in significant amounts. These include sulphates, calcium, bicarbonates and magnesium. All these elements come from the dissolution of various rocks by water flowing through the subsoil.
Only one minor or trace element is shown on the notice board. This is iron, present at 0.6 mg/L. Other trace elements have been identified thanks to the work of the geologist Poulain (1977) and later by M. Grimaud (1987). These trace elements, also known as trace elements, are essential for the proper functioning of the body. They also include fluoride, silica, lithium, zinc, cesium, etc., all in perfectly assimilable form, provided that the water is not altered.
In his 1947 thesis, Dr Lesbros also reported radioactivity due to the emanation of radon, a common phenomenon in hot springs. This natural radioactivity, which has stimulating properties, was promoted by the major spa stations as early as the 1930s, particularly on advertising posters. Other gases may also be present, such as carbon dioxide, nitrogen and hydrogen sulphide.
The therapeutic virtues of this spring have been confirmed by various studies.
As early as 1784, Major Charmeuil, a surgeon at the Mont-Dauphin military hospital, published his work in the Journal de médecine et chirurgie militaires. According to him, these miraculous waters cured all illnesses.
In 1947, Dr Lesbros confirmed these claims. They were said to have a beneficial effect on respiratory, kidney and liver diseases, dermatitis, rheumatism, arthritis and so on.
The Réotier petrifying fountain and its hot spring
This time we’re on the opposite bank of the Durance, 2 km from Plan de Phazy. After a ten-minute walk from a car park, you can admire a petrifying fountain known since ancient times.
A true work of art, this fountain depicts an imposing monster’s mouth.
In fact, we know that it attracted many visitors even then.
In 1889, during the construction of a railway line, several hundred Roman coins were found at the foot of the fountain.
It was situated also on the Roman road between Arles and Rome.
How did such a thing come into being?
Generally speaking, the formation of calcareous concretions that petrify their surroundings can be explained by the following process. Firstly, the presence of certain elements dissolved in the thermal water is necessary. These elements, calcium, magnesium and bicarbonate, must be present in ionic form. In addition, these elements should precipitate when certain gases dissolved in the water, in particular carbon dioxide, are released.
However, scientific research suggests that the formation of these minerals is probably more complex than a simple chemical reaction. These calcareous concretions could also be the work of micro-organisms.
Finally, this spring water has a lower mineral content (5 g/l) than La Rotonde (7 g/l), and a temperature of 20°C. Renowned for its many therapeutic virtues, it is also used by the L’OCCITANE laboratory to formulate some of its products.
