Urban Trawl: Plymouth

When you arrive, it's blocked off by a car park, and shadowed by a clearly once shiny but now greying glass office block; but you find it soon enough. It starts with a series of underpasses. These aren't your common or garden subways, but wide open things, a sort of combination of underpass and grand public square. Pass under them and you're right in the middle of an axis, flanked by large, severe Portland stone buildings. The space is vast, something which subsequent planners have tried to efface via everything from funfairs to gardens to giant TV screens. Stylistically, this boulevard is not quite classical, but not quite modernist either; for that, you must walk all the way to the end, where you'll find two towers – one, the elegant and well-made Civic Centre, now almost derelict, the other, a bland and shoddy Holiday Inn, very much occupied. Then you're at a wide public park looking out over a glorious waterfront, a view of warships, rolling green hills and rocky Cornish cliffs, with a lighthouse, a lido, and an art deco war memorial for company. This is Armada Way, the main street of Plymouth city centre.

It's the axial fulcrum of a comprehensive plan, in the British city more damaged than any other by Luftwaffe attacks. Patrick Abercrombie's plan was not especially avant-garde – certainly a lot less so than his plans for London – and nor was the architecture. It's in a style which is as yet un-named, some sort of Attlee—Scando-Stalino-classicism, which anyone familiar with The Moor in Sheffield or Above Bar in Southampton will recognise, though it is superior to both. Architecturally, it lacks the futurity of near-contemporaries such as London's ultramodernist Churchill Gardens or populist Lansbury Estate, or the multilevel replanning of Coventry. Its compatriots are elsewhere – August Perret's Le Havre, or, rather more controversially, post-war East Berlin or Warsaw. A big boulevard, for the tanks to go down (this is a garrison town after all) symmetrical stone buildings, ceremonial plazas. It's not what 1950s critics considered the architecture of democracy. At this distance, however, its insistence on the traditional street seems more contemporary, as does its continental nature - a space seemingly designed for cafes to spill out onto the pavement, which they do. If, for Aldo Rossi, the Stalinallee was 'Europe's last great street', then Armada Way is certainly Britain's last.

It's also a counterfactual in stone. Abercrombie's Plymouth is what might have happened everywhere in the UK if proper, ideological CIAM modernism had never enjoyed its brief moment of planning hegemony. Its driving ideas are those of inter-war, twilight-of-empire Britain, as are its architects – Thomas Tait, William Crabtree, Louis de Soissons, Giles Gilbert Scott. The influences of Lutyens and Charles Holden are also palpable. It's curious that Gavin Stamp, for instance, has recently repeated the claim that 1940s-50s Plymouth brought little of value to replace the destroyed city, given that it represents exactly what he has been arguing for in British architecture and planning for some decades. These dignified masonry buildings, in a non-dogmatic classical tradition, are as equally far from Le Corbusier and Leon Krier. But funnily enough, central Plymouth is seemingly held in no greater public affection than the more hardline Coventry or Sheffield. Invariably, the plan is described as a 'concrete jungle' in circles non-architectural, despite the fact that the dominant materials are Portland Stone, granite and brick. It's a reminder that modernity and planning itself, not its stylistic vagaries, are what offend a certain kind of British psyche. It is not pretty. Cohesive it may be, but central Plymouth does not look like Bath, and some will never forgive it that fact.

What it does prove, however, is that this modernised classicism was tired by the late 1940s. Some individual buildings do impress – the two stepped department stores which provide the axis' main focus, by Tait and Alec French, are loomingly powerful as anything from the 1930s, and B.C Sherren's National Provincial Bank is lovely, albeit remarkably similar to the precisely contemporary Finland Station in Leningrad – but overall the cohesiveness, planting and sheer generosity of space are what is really of value here. The architecture is palpably an aesthetics in its dotage. In a very prominent place is Giles Gilbert Scott's last completed church, a sadly wan, provincial design from the architect of Battersea and Liverpool. In some ways, central Plymouth is a reminder of just how necessary modernism was. Slightly later structures like the Civic Centre and the wonderful Pannier Market reflect this, especially the whale-like concrete interior of the latter. After the 1960s, the grand civic gesture sometimes continued in a different form; Peter Moro's late 1970s Theatre Royal is central Plymouth's only Brutalist building, and an excellent one, its geometrical complexity and harsh volumes akin more to Moro's ex-Tecton partner Lasdun than his own more clipped work. Nearby, The Pavilions is a messily ambitious structure where pedways link a swimming pool to a car park, shopping and then back to the Abercrombie centre, a laudably ambitious undertaking marred by cheap and nasty '80s retail detailing.

So much for the planned centre. Plymouth is lucky enough to have both one of the UK's most complete pieces of grand city planning and one of the most interesting, albeit sanitised, areas of ad hoc inner-urban townscape. Walk round the breathtaking panorama of the Hoe past an inadvertently proto-Brutalist fortress, and you're in the Barbican, an area once slated for demolition full of snickets, strange and surprising vernacular architecture and, interestingly, very sensitive modernist infill. Plymouth evidently had one of the best post-war City Architects in HJW Stirling, and his Paton Wilson Quadrant is a lovely council estate of lush, bright stone, tile-hanging, Swedish details and easy informality, a remarkable contrast with the Hausmannian melodrama a few yards away. Sadly all this cleverness and warmth gives way further along Sutton Harbour to the luxury architecture of the 1990s and 2000s, with several more-or-less miserable blocks of flats, here particularly unimpressive and badly made. Sometime in the 1970s or 1980s, Plymouth seemed to lose all its confidence, seemed to start to hate itself. It's a familiar enough story in the north of England, and deindustrialised, poor, shabby but often glorious old Plymouth has more in common with a Bradford or a Liverpool than with the seaside, spa and silicone towns of the south.

The last of the modernist buildings in Plymouth is an apartment block, Ocean Court, an elegant and faintly 70s sci-fi irregular ziggurat. It's the sort of thing you might normally find in Benidorm, and it points to one of the two ideas for contemporary Plymouth – luxury waterside living. Opposite, in Stonehouse, is Urban Splash's atypically sensitive conversion of John Rennie's King William Victualling Yard into flats; adjacent are a couple of surviving sheds putting together warships and yachts, as other dock buildings are assigned to a different social class.

In the centre, redevelopment is neither as elegant as here in Stonehouse nor as identikit as around Sutton Harbour – instead there are two structures which have a good pop at the 'iconic'. There's Chapman Taylor's notorious Drake Circus mall, which swallows a chunk of Abercrombie Portland Stone street, but is most embarrassing for the way it axially frames the bombed-out Charles Church with trespa wafers, and for the lumpen car park which faces a 'public' square; facing that is Henning Larsen's Roland Levinsky Building for the University. With its combination of gestural vernacular and angular Regen shape-making, it's of its time, though it genuinely attempts to make something of its prominent site, a decent attempt at civic presence. These two make a little effort, one with some success and one with much bathos, to create something specific to Plymouth. Much more typical are the little encroachments into the planned centre, all of an extremely low quality – prefab hotels, already dated Blairite apartment blocks, a miserable little casino. More encouragingly, its rigid zoning is being lifted – one of Tait's great towers is now student flats, inadvertently giving ubiquitous developers Unite their only architecturally notable building.

The planned post-war Plymouth is now being recognised as being of value, with publications, listings and possible conservation areas. It's about time that social democratic Britain was the subject of something more than giggling and ridicule, and there's no doubt that the incremental demolitions around the edges of the place and their replacement with dross should be stopped. Yet the notion the centre could become an object for Keep Calm and Carry On austerity tourism forgets that naval tourism already exists here, and hasn't exactly reversed the city's decline. Plymouth already has its post-industrial leisure, its riverside galleries and loft conversions, and yet remains poor. It needs new ideas. But as a place to come and think about alternatives, you could do a lot worse than this forlorn, bracing city.