The Fort de l'Ecluse is located approximately half way between Bellegarde-sur-Valserine and Geneva, high above the River Rhône and the main road between the 2 towns.  In the past this was a very strategic point between the Kingdom of France, the Dukedom of Savoy and the city of Geneva and ownership of the fort changed hands many times over the centuries.  

The fort bears witness to military architecture down through the ages with its watchtowers, arrow slits, turrets, high walls, bunkers and magazine.  The Fort de l'Ecluse was completely renovated during the 19th century.  During these works, the fort's best known feature, the underground passageway with its 1,165 steps between the upper and lower fort, was built.

Today there are guided visits available which describe the harsh conditions of daily life the soldiers who manned the fort endured.  There is also a museum within its walls and many events take place there during the summer.  Additionally the Fort de l'Ecluse has some spectacular views of the Rhône Valley below.