The Gros Ouvrage at Cap Martin was the most southerly in the chain of Maginot forts. It lies overlooking the Mediterranean Sea and has a surprisingly urban setting. It comprises three fighting blocks - two artilllery and one with lighter weapons. It has a lower level gallery with a 60cm railway; steps and ammunition hoists ascend to the fighting blocks; this layout is more typical of the central Maginot forts than the Alpine sector. It had a garrison of around 350.
The fort was attacked by the Italians in June 1940 but the fort was not breached and the Italians retreated when the surface of the fort was bombarded by neighbouring forts. Retreating German troops destryed block 3 in August 1944 to prrevent it being used against them. The fort was been partially restored by a local organisation and is open for visits on Saturdays in summer months.