With Les vacances de Monsieur Hulot, in 1951, Jacques Tati was perhaps the first personality to present a brighter picture of an otherwise somewhat gloomy Saint-Nazaire. Albeit in ironic and melancholy tones, the film gave the Breton city the air of being more of a seaside holiday location. It helped to redeem its image, rooted in the minds of the French themselves as a dull place with a difficult history: a city of sailors and of workers employed in its local heavy industries, afflicted with rough Atlantic weather and almost totally destroyed by World War II. It also holds the sad record of having been the last city to be liberated in Europe, three days after the signing of the armistice in Berlin.

Today, the slogan adopted by the city council in its pledge to boost interest in local attractions and resources is "Saint-Nazaire: l'énergie Atlantique est là". Competition with its rapidly developing neighbour Nantes is also a big factor in the publicity drive. The catchphrase nicely sums up the revitalisation programme that the small city on the Loire estuary launched in 1990 with its Projet Global de Développement. After a long period of crisis and with admirable far-sightedness, its administrators set out to rethink the framework of the city's physical urban expansion, the strengthening of its main industrial resources (naval shipyards and aeronautical works), and new prospects for social and cultural life.

In recent years, the 67,000 inhabitants of Saint-Nazaire have witnessed an expansion of residential and tertiary areas and their related services and infrastructure, plus an experimental effort to reconnect the city centre to its truly vocational maritime strip. Furthermore, they have shared an articulated system of cultural initiatives that centred mainly on the contemporary and have been cleverly filtered into the existing built fabric. No major eye-catching architectural attraction has been commissioned to contain the numerous projects aimed at a differentiated public. Instead they have all been adequately housed in suitably converted historic buildings. One need only mention the annual world music festival Les Escales, which draws up to 40,000 spectators; the Fanal, an acclaimed centre for performances of theatre, song, circus, variety and dance; and the Grand Café and its services to contemporary art; or the Meet (house for foreign writers and translators), where international intellectuals gather to exchange views.

In this sense the mental, not the physical landscape of Saint-Nazaire has been transformed. The Bilbao model was rejected in favour of the easier but also conceptually subtler line previously pursued in Paris at the Palais de Tokyo, refurbished with invisible touches by Lacaton & Vassal as an interdisciplinary place dedicated to contemporary creation; or that of Karlsruhe and its ZKM, the Centre for arts and media, installed in a substantially unaltered ex-arms and munitions factory.

In Saint-Nazaire there is one particular old building, situated in the port, which as part of this cultural strategy of circular reuse has now been reintegrated into the life of the city after years of abandonment. A monument sui generis, it comprises a 480,000- cubic-metre concrete block, cast in a parallelepiped 299 metres long, 124 metres wide and 18 metres high. Instantly identifiable as a bunker, it was built by the German navy during World War II as one of its most important U-boat bases along the Atlantic coast of occupied France.

This impenetrable obstacle between the city and the sea is, in the opinion of many, an "uneasy" place. The building today projects the forceful image of a metaphor, clearly seized by local government when gauging the possibility of its inclusion and reuse. Back in 1998, Manuel de Solá- Morales, winner of a competition for the area, had envisioned its reuse as a public facility to be opened towards the sea, with shopping and eating areas, a large car park and a street ramp leading up to a practicable roof. Only some of these proposals were later realised, such as access to the roof, perhaps its most significant urban feature. But the city council's vision has remained consistent since then, though with more realistic compromises to allow real improvements and progressive transformations of the complex identified by phases, with works expected to be completed by 2012.

In 2003 a new competition focused on the so-called "Alvéole 14", one of the floating dock berths for two submarines, with service rooms on the landside. The brief specified the creation of a LiFE unit (International Place of Emergent Forms) and a VIP room (stage for performances of contemporary music), with a total surface area of 5,500 square metres.

The young Franco-Berliner firm LIN, formed by winners Finn Geipel and Giulia Andi, has interpreted the historical memory of the place with respectful awareness, by working on the present enigmatic nature of its spaces and on the simplicity of their circulation. A wide straight promenade, identified by a regular and light rain of suspended lights, distributes with silent discretion the "caves" of thick reinforced concrete that have remained in their brutally original state – infiltrations of water and old writings included. This inner street, which also in the original design ran perpendicular to all 14 dry docks, still shows traces of the rail tracks that carried wagons transporting heavy equipment.

There are almost no newly superimposed elements at all in the project, apart from the odd metal staircase or systems pipes. An air of liberating detachment can be sensed. Any ethical question of whether or not to conserve and reuse episodes of Nazi history is brushed aside, even though the issue is to this day a deeply contentious one among German as well as other historians and politicians. The LIN project, however, has added a pleasantly refreshing surprise among so much rigour. Mounted on the roof of the Alvéole 14 section is a translucent, geodetic cupola, transferred from Berlin's Tempelhof airport where it had housed a disused radar. At Saint-Nazaire it is now a think tank, a compact experimental laboratory. Illuminated by night, it signals to the city that something new has happened in the bunker.