The Welsh assembly's home looks like an 'effete tent', according to Mr Jenkins
Author and journalist Simon Jenkins has attacked the "missed opportunity" of the redevelopment of Cardiff Bay.
This had led to the Wales Millennium Centre and Senedd being built in Cardiff Bay, while the Millennium Stadium was left in the city centre.
Jenkins, now chairman of the National Trust, told the Hay Festival planners should have decided just the opposite.
He criticised the new Welsh assembly building as an "effete tent which looks just like it has arrived from Arabia".
The writer praised the Millennium Stadium itself but said stadiums meant "death" to city centres, and the rightful home of the assembly should have been the City Hall amid Cardiff's "great civic buildings".
Jenkins was keen to tell the audience in the border town festival that he was half Welsh through a father who was from Dowlais in Merthyr Tydfil.
He was discussing his latest book on Welsh historic buildings which tries to uncover the basic themes of Welsh architecture.
He said he felt the answer to this lay essentially in the lost, ancient, small, rural churches of Wales and the chapels of the industrial revolution.
Jenkins said he very much favoured the restoration of crumbling old buildings and castles as long as it was done with sensitivity.
He lamented the fact that many ancient buildings were inaccessible to the public, saying: "Wales has 300 castles of which five you can go into."
He said: "I would like to see us doing what the Victorians did and taking some of these great castles and restoring them."
Jenkins said Wales was one of the most beautiful countries in Europe and in researching the book he has been "left with an incontrovertible sense that Wales is a country and not a region of England".
But he lamented the destruction of many of Wales' old terraced streets and urged people to get involved to save their architectural heritage.