To read what some commentators have written about An Bord Pleanala's landmark decision to refuse planning permission for the massive development proposed for Spencer Dock, you might think that Ireland was mindlessly turning its back on the 21st century.

Yet the decision, and the mammoth planning inspectors' report that informed it, implied nothing of the sort. In fact, if anything, it was a vindication of architecture and urban design in the context of a European capital city - and few architects practising in Dublin or anywhere else in Ireland would disagree with it.

"We can all sleep more easily in our beds tonight," one Dublin-based architect sighed happily on the day the ruling was announced. The appeals board may have used more polite language than Bertie Ahern's "monstrosity" remark, but there can be no doubt that its members viewed the scheme in much the same vein.

The board's decision to grant planning permission solely for the National Conference Centre may be seen as political; indeed, Government policy was cited as one of the reasons for doing so. But the board saw no compelling case for the over-blown master plan devised by Kevin Roche at the behest of his clients.

Quite apart from design issues, Spencer Dock went down in flames because the vast bulk of the scheme put forward by the Treasury Holdings-led consortium was premature, as the board said, pending resolution of the alignment for a new, strategically-important cross-river rail link east of the existing Loop Line.

Secondly, "its scale, bulk, mass and campus-style layout would constitute an inappropriate urban form of development for Dublin". What was proposed, according to Karl Kent, one of the senior planning inspectors on the case, was "a free-standing entity, which happens to stand in the docklands of Dublin but could be anywhere".

Mr Kent's contribution to the mammoth report on Spencer Dock - co-ordinated by Des Johnson, who presided at the 16-day oral hearing last March - deals in detail with the architectural and urban design issues that informed the board's decision and, unusually, it is peppered with photographs of major schemes elsewhere in Europe.

In Mr Kent's view, Roche Dinkeloo's master plan had been generated largely by the developers' requirement to achieve a predetermined floor area of six million square feet. This was "difficult to sustain if the overall design is not satisfactory", which it clearly was not. Quite simply, it would have been the wrong way to go for Dublin.

As others had argued, its form - free-standing, high-rise buildings on a podium - "could reasonably be regarded as owing much to American city models", and did not lend itself to the design changes that would inevitably arise over the years, unlike a "less assertive" and more traditional European city block development.

"In an international context, the proposed development at Spencer Dock is not especially high, particularly compared with cities in the USA or the Far East," as Mr Kent put it. However, the proposed buildings were "quite high in the context of Dublin", as illustrated so tellingly by the 1:1,000 scale model showing it in context.

Height, which was not specifically mentioned in the ruling, is one thing. Bulk and mass are another. And compared to the slenderness of Liberty Hall or the "pompously titled" Millennium Tower in the Grand Canal Docks, the proposed buildings were "quite massive" making it unlikely that the scheme would be perceived as an urban design success.

"The foregoing remarks should not be taken as excluding the option of tall, slender buildings, as sought by the City Architect. If high buildings are to be developed in Dublin, it should be preferably on the basis of a proper plan. It is important that the city should avoid the mistakes evident in English cities, including London," Mr Kent said.

In Frankfurt, where some of the tallest buildings in Europe are located, "a conscious decision was made to allow this type of development". However, the impact of this "mini-Manhattan" was "fairly positive" due to "the contrast between the great height of these slim structures and the traditional scale of the surrounding buildings".

There was no reason why the heights of buildings on the Spencer Dock site should "follow rigidly" the pattern set by the Dublin Docklands Development Authority in developing the extended IFSC site. In the inspector's view, the scale of the buildings in its second phase was "somewhat too low" and could have been "modestly increased".

As for Kevin Roche's National Conference Centre, he said it had been "designed from the inside out," resulting in "a large box, relieved by the glass cylinder on its frontage". Both high (slightly less than Liberty Hall) and massive, this "severe, if striking, building" would "greatly exceed the scale of anything along the river frontage of Dublin".

But given the civic importance of the NCC, its "strong geometry" and its location overlooking a wide section of the river, Mr Kent considered that it would be generally successful in the wider context of the Liffey Quays. Opening up the building to the canalside might also help to relieve its '"rather monolithic" quality, at least to some extent.

And though the developers had put great reliance on Kevin Roche's "excellent reputation", implying that the future development of Spencer Dock should be "taken on trust", the Irish-born, US-based architect (aged 77) told the oral hearing that he would only be taking detailed design responsibility for the NCC and not for the other buildings.

Much hay was made of the high proportion of open space, amounting to 25 per cent of the overall site. But Mr Kent found that most of it "consists of areas between buildings rather than areas formed by buildings" and thus lacked definition and enclosure. He also concluded that sheer-faced tower blocks would not be suitable for family housing.

The inspector believed it was likely that the 51-acre site, largely owned by CIE, would be "developed over many years and by many different architects and possibly different developers". In that context, it would need "a strong overall direction, based on a plan" along the lines of the DDDA's area action plan for the Grand Canal Docks.

Dublin Corporation's decision last August to cap the overall floorspace at 4.6 million square feet had "jettisoned" Roche Dinkeloo's master plan, replacing it with a number of written conditions that were open to interpretation. This "does not stand up", Mr Kent said, because it could not guarantee a high quality architectural/urban design solution.

His report cited Potsdamer Platz in Berlin as the most significant urban redevelopment in recent years in Europe. A dense, large-scale, mixed use scheme, it was relatively low-rise (eight to 10 storeys) but with some taller buildings (up to 20 storeys) at points of emphasis. It was also based on the street and block pattern of the European city.

YET Spencer Dock would have put Potsdamer Platz in the shade, with almost one million square feet more floorspace than the biggest scheme in Berlin. That is a measure of the extent to which the developers lost the run of themselves, just as the 921-page inspectors' report is a benchmark of this monumental waste of time, effort and money.

"Arguments based on the claimed importance of Dublin in the world economy should be treated with some caution," according to Mr Kent. Though the city has become an important offshore banking and computer software centre, "it is not likely to be in direct competition with major financial centres such as London or Frankfurt".

It is also clear from the very thorough planning assessment and from An Bord Pleanala's decision that the design of any new scheme for Spencer Dock will have to take account of its impact on the Fitzwilliam Street "Georgian Mile" vista as well as the guidelines on high buildings due to be published shortly by a now-chastened corporation.