Combined ticket with Fort l'Écluse

Fort l'Écluse, Fort de l'Écluse or formerly Fort de la Cluse is a military fort built into the mountainside in the commune of Léaz in the Ain department in the Auvergne-Rhône-Alpes region, named after the Écluse defile which it dominates, offering an incredible view of the Rhône from its right bank. The narrow cluse  used by the Rhône winds its way between the Grand Crêt d'Eau (north-west) and the Vuache mountains (south-east). The gorge closes off the Geneva basin to the south-west, making it a strategic natural passageway.

Fort l'Écluse is open from 10.30 am to 6.30 pm:

• weekends in June
• every day in July and August
• weekends until the European Heritage Days

Guided tours for groups are available outside these periods, but must be booked in advance.Exhibitions are held in the lower fort, and a wide range of events are organised for the public (theatre and concerts, including the Jazz in Fort l'Écluse festival).Access to the terraces beneath the upper fort is by climbing the 830 steps in the gallery carved out of the rock! Since 2017, the upper fort has been home to an adventure trail.

A twin ticket priced at €12 is available during the summer season when Fort l'Écluse is open.

The twin ticket can be purchased directly from the Chateau ticket office.

The Fort has stood the test of time and war

Its history dates back to Roman times when, in 58 BC, Julius Caesar had the "Caesar Tower" and an enclosure built to protect himself from the Helvetians. In 600 AD, the parish of La Cluse was created by the abbey of Saint-Claude. In 1225, the abbot of Saint-Claude ceded the Pas de la Cluse to Amédée II, baron of Gex. He set up a fortified house to collect tolls. The fortified house found itself at the heart of the feudal war between the county of Savoie and the Dauphiné. In 1293, the fortified house and its tolls were sold to Amédée V. In the 16th century, the Pas de la Cluse was once again at the heart of the territorial disputes between the Duchy of Savoie and France, and the Treaty of Lyon signed in 1601 put an end to the war between Savoie and France.

During Napoleon's wars against Europe, the Fort was occupied and led to the capture of Fort l'Écluse on 1 March 1814 by General Bardet's men, while the Fort was defended by an Austrian garrison. The fort was virtually destroyed in 1815, and between 1820 and 1846 an upper fort was built above the first, to prevent attacks from the top of the mountain.

The two forts were linked by an underground staircase with 1165 steps, and the current road tunnel under the Vuache mountain was built during the Second World War. From 1935 to 1945, the fort was defended against the German army by Captain Favre and his men.1960 saw the abandonment of the fort and its military activity. The fort deteriorated. 

It was purchased in 1982 and then managed by the Fort l'Écluse Animation association, before becoming the property of the Pays de Gex Communauté de communes (now Pays de Gex Agglo) in 1997. It has been managed by its cultural department since 2008.