Fort de Tournoux The Fort de Tournoux is a fortification complex in the Ubaye Valley in the French Alps . It was built between 1843 and the early 20th century to defend France against invasion from Italy and Savoy . It was described as the " Military Versailles of the 19th century , " resembling a Tibetan monastery on the mountainside above the Ubaye . The fort is actually an ensemble of fortifications , including some " batteries " that rival the main fort in size and power . Prehistory . Earliest records show that the position of the village of Tournoux was a strategically important one , with the tiny plateau offering food and watering facilities to armies crossing the Col de Larche from modern day Italy and the Col de Vars . There is evidence of Roman occupation of the plateau . Of later times little survives , but there are the traces of a 7th - century fortified church in the valley . Between the 7th century and the 17th century , the upper Ubaye Valley changed hands between states about 17 times – usually because either the Col de Larche or the Col de Vars became snowless first , and whichever side was nearest was able to march in while the other sat waiting for the snow to melt . In the 18th century , the valley finally became part of France and the first proper fortifications were built . Three redoubts , of which the Redoubt de Berwick still remains ( albeit in modified form ) , were constructed as shelters for garrisons of soldiers . At the time , the use of cannons was relatively limited and such fighting as there was would have been hand - to - hand or musket - fire only , with the presence of the soldiers being the major deterrent to invasion over the cols . Layout . Caserne , Fort Moyen and Fort Supérieur . The Fort de Tournoux is constructed more - or - less continuously up the side of the mountain from altitude to in several levels . The lowest level is the barracks ( Caserne Pellegrin ) at 1300m next to the main road from the Cols ( Larche and Vars ) to the village of la Condamine and the towns of Jausiers and Barcelonnette . A battery at this level , built between 1846 and 1862 , is called Batterie XII . Linking these with the Fort Moyen ( " middle fort " , also known as Fort Grouchy ) is a road , constructed to allow mules to ascend with carts – so at a maximum gradient of 10 % with frequent hairpin turns . The hairpins were constructed so that the mules could park their double - ended carts and run - around to pull the cart in the opposite direction up the next stretch , thus avoiding the need to turn around the hairpin bends , which often caused carts to topple over and spill their contents . The Caserne Pellegrin and the Fort Moyen are also linked by an enormous staircase with over 1000 steps which was constructed in the rock , with windows opening onto the “ French ” side of the fort and batteries ( notably the B - douze — B12 ) facing the passes . The windows provided light and air and were also used for the removal of spoil from the tunnels . Finally there is a cableway that allowed stores to be carried to the Fort Moyen which was installed after the fort was electrified in 1908 . From the Fort Moyen is a serpentine road that hugs the mountainside up to the Fort Supérieur . Above this there is another underground passage that links further up still to the Batterie du Clos des Caurres . Above this still is the Observatoire and Batterie de Serre de l ’ Aut at the top of the mountain . There is a covered roadway that links the Fort Moyen with the village of Tournoux , providing another means of entry and exit – this way is very heavily protected with loopholes and gun emplacements . The Fort Supérieur and the Batterie du Clos des Caurres are protected by a scarp / counterscarp wall system and by sliding drawbridges , which withdraw into the guardhouse on rollers when closed to traffic . These are simple enough to be operated by two people with very little effort , even after 50 + years of no maintenance . The total cost of the fort had been envisaged at about 1 . 5 million francs ( in the money of the time ) but the final cost was over 3 . 5 million , causing a huge hole in the government finances at the time . Armament . The main fort in 1940 contained relatively little in the way of armament : three 81mm mortars were located in Fort Moyen , firing to the east , while two 81mm mortars , also firing to the east , and two 95mm guns firing to the northeast along the valley , were located in Batterie XII at the level of the barracks . An anti - aircraft battery was located in Fort Supérieur . Four 155mm guns were located in Tournoux itself , to the northeast . A project to locate three 145mm guns in a casemate in Fort Grouchy firing towards the Col de Larche was proposed in 1929 , but not pursued . Another project , to outfit Batterie XII with four 155mm guns was started in 1931 and completed in 1934 , but the armament was never installed . Batterie du Clos des Caures . The Batterie du Clos des Caurres is even higher than Fort Supérieur , at and contains the main armament of the complex . Built between 1879 and 1881 , the Séré de Rivières system fort was planned to mount six de Bange 155mm guns . The underground gallery linking to Fort Supérieur was completed between 1880 and 1883 . The deep ditch around the position was completed in 1890 , and from then until 1897 a wall was built connecting to Fort Supérieur . The position was manned by 656 men under 7 officers . Prior to World War I , efforts were made to provide concrete cover over critical areas , which were not completed in 1914 . A casemate for two 75mm guns was built to cover the flank of the Vallon Claus battery , and the fort was re - armed with eight 95mm guns and four 120 mm guns . Other sources give an armament of four 75mm guns , four 155mm guns and three 81mm mortars . Fort de Serre de l ' Aut . The small Fort de Serre de l ' Aut was built 1890 - 1893 as an outpost on the edge of a cliff to the west of the main complex at . It is connected to the main Fort Tournoux complex by a military road . Armament consisted of four 95mm guns Batterie du Vallon Claus . The Batterie du Vallon Claus is located to the north of the main complex . Built 1880 - 85 , the battery is a walled mountaintop enclosure with a series of observation posts extending to the west . It was armed with two to six 75mm guns . The garrison comprised 75 men , housed in a barracks nearby , connected to the main fort via a subterranean ammunition magazine . The battery covered the entrance to the Maurin valley and the small valley of Plate Lombard . The four observation posts are known as the Lignes des Abrupts . At an altitude varying from to , the posts are simple , nearly square buildings with no permanent armament . Stages in construction . Begun in 1843 , the Fort Moyenne and Fort Supérieur were constructed over a 20 year period . The construction of Fort Moyenne spanned 1846 - 1862 , and Fort Supérieure 1852 - 1860 . The B12 and the underground stairway were also constructed at this time . The purpose of the fort was to lock the access to the Ubaye valley from the Cols , and the fort was so positioned to allow covering fire from the bronze cannons firing round shot that were installed there . With a range of 3 - 400m , these cannons were able to cover the roads ( well , tracks ) coming down from the Col de Vars and the Col de Larche , as well as the upper Ubaye valley . Looking from the B12 , one can see what an excellent prospect of the valleys this afforded . Cannons were also installed at batteries on the eastern side of the Fort Moyenne and the Fort Supérieur . The main building materials were faced stone – Ubaye marble , used for load - bearing structures and for decoration – and the local stone , hewed from the mountain itself , used as a rough construction material along with lime mortar . The fort was designed and built by the French Army engineering regiment – the " Genie " with some help from local labourers – many of whom worked as blacksmiths , carpenters and stonemasons – this was more profitable to them than working the fields . The local economy also benefited from the presence of the forts and the army , both during construction and afterwards , the villages of la Condamine and Gleizolles in particular . By 1860 , improvements in artillery , particularly the replacement of the bronze cannon with steel , rifled guns firing pointed , exploding , shells gave the opportunity for accurate fire over much longer ranges . Typical guns at the time could hit targets 8 – 9 km away . The decision was made to create extra batteries above the Fort Supérieur — the Batterie des Caurres and the Batterie de Serre de l ’ Aut . These gave a much better firing line for engaging targets earlier in their approach over the cols and with the Observatoire de Serre de l ’ Aut at the top of the mountain meant that the fort was able to secure the valley in a very efficient manner . In the 1880s further improvements in artillery demanded additional upgrades , resulting in the batteries of Vyraisse , Mallemort , Cuguret and the nearby Fort Roche - la - Croix , which later became the basis of the Maginot Ouvrage Roche - la - Croix . By the end of the First World War advances in military technology meant that the defences of the fort were improved with concrete and the usage of the fort changed somewhat . In the 1920s and 30s , several Maginot Line forts were built , on either side of the Col de Larche at Roche - la - Croix ( south side ) and St - Ours ( north side ) . As mentioned below , these were linked by telegraph to the Fort de Tournoux . Complement . The fort supported a complement of 900 officers and men , who were barracked in the Caserne Pellegrin at the base of the fort and in the Fort Moyenne . Looking at the Fort Moyenne in the pictures , the left - hand building was for the soldiers and NCO ’ s , the right - hand building for the officers . The buildings were supplied with piped drinking water from a “ source captee ” at the top of the mountain , which fed huge tanks at the Fort Supérieur and the Fort Moyenne . Electricity came to the fort in 1908 . Communications were originally by a form of semaphore from mountain - top to mountain - top , but eventually a cable - telegraph was installed linking all the mountain - forts in the area , Fort de Tournoux being the hub for this network . At the back of the main barrack buildings are wide , protected walkways ( the buildings had staircases but no internal corridors ) with access to each room via the walkways and landings on the back of each building . The protected thoroughfare was designed to provide natural ventilation to the buildings to prevent damp – a very successful design feature . Above the buildings are various workshops and magazines . The magazines are interesting because they are built as buildings within buildings , to minimise damp and increase the flow of air around the munitions . The floors are nailed with bronze nails , to minimise sparks . Above the entrance roadway and the soldiers ’ barrack block are arched structures ( looking a bit like tall , thin bridges ) attached to the rock face . These were built to catch rocks released by freeze - thaw erosion of the rock face above . Some of these fallen rocks were collected and used for further construction of the fort . Action . The fort saw action during the Second World War . It was attacked by Benito Mussolini ’ s fascist forces on the day that Adolf Hitler entered Paris — fighting ensued for three days , but was cut short by the fall of France . Later in the war , in October 1944 the fort was occupied by the German army as Free French forces approached up the Ubaye valley from their invasion in southern France . As the French got closer , the Germans destroyed the water and electricity supplies and looted much of the fittings of the fort for firewood etc . They then occupied the Maginot forts nearby and holed - up for the winter . The French Army spent the very cold winter of 1944 - 45 in the Fort de Tournoux , before finally attacking the Germans and extracting them from the Maginot ouvrages in April 1945 . Decommissioning . The French Army occupied the fort until 1947 , leaving only the B12 to be used as an arms store for the Regiment in Barcelonnette . This was eventually decommissioned in 1989 . Later history From 1947 until 1991 , the fort was generally left to the vandals and graffiti artists . The fort was left with its Domaine Militaire signs to scare away potential explorers , and the Fort Supérieur was well protected by its walls and barbed wire . Thus the forts remained in a fairly good state of repair ( although open to the elements ) until purchase from the military by the local government . Preservation . Since 1991 , the local authority has done some renovation work on the fort , with new roofs on the main blocks at the Fort Moyen and some shoring - up work in the tunnels at the Fort Supérieur . The gates to the fort are now locked and protected and excellent guided tours are a regular occurrence in the summer . The Batterie des Caurres now has an up to date use as a relay for TV and mobile phone signals to the local area . The Observatoire is still used for a similar purpose ; possibly by the military ( this is unclear at the moment ) . Update 2012 : it seems from Google Streetview images that some of the building at the foot of the Fort have been razed ( unsurprisingly , since derelict but it does rather spoil the atmosphere of the lowest level ! )