Between phases, the National Assembly changed contractors and the project's management structure, but retained Lord Rogers of Riverside as the scheme architect.

Cardiff Docks had been the largest coal-exporting port in the world, but by the 1980s with the decline of the south Wales coalfield, the area had gradually become derelict.

Rather it would be a transparent envelope, looking outwards to Cardiff Bay and beyond, making visible the inner workings of the Assembly and encouraging public participation in the democratic process.

"[5] The main area in the building is the debating chamber, called the Siambr, including a public viewing gallery.

[16] Yr Oriel ("The Gallery", from Old French: Oriol;[17] Welsh pronunciation: [/ɔrjɛl/]) is a public sitting and exhibition area with views down to Y Siambr and committee rooms.

[18] The Swan chairs selected for the Neuadd and Oriel areas were from Fritz Hansen, a Danish company, and originally designed by Arne Jacobsen in 1958.

The Swansea-based artist Alexander Beleschenko[23] designed and created the circular and domed Heart of Wales for the centre of the Siambr.

It has five parallel rows of 32 glass plates and was designed to have the practical use of protecting the public from high winds coming off Cardiff Bay.

The Government of Wales Act 1998 was passed by the Parliament of the United Kingdom, and was granted Royal Assent on 31 July 1998.

[39] The Welsh Office concluded that Cardiff City Hall would only remain an option if the initial costs were £17M or less, which was the top end of the estimate figure given in the White Paper.

[39] There were discussions between the leader of Cardiff Council, Russell Goodway, and the Secretary of State for Wales, Ron Davies MP.

All the proposals were reviewed by the Welsh Office, who rejected sites due to poor location, accommodation or cost.

[39] The site was acquired by the National Assembly from Grosvenor Waterside Investments Ltd, which was owned by Associated British Ports.

[39] Before deciding on Capital Waterside as the site of the National Assembly, Davies announced on 13 March 1998 that an international competition would be held to select the design of the building for the debating chamber.

[39] Richard Rogers said, "The idea was that steps rise out of the water and there is a whole public domain where people meet each other and look down on the Assembly Members.

"[45] Richard Rogers had previously designed the Lloyd's building in London and the Pompidou Centre in Paris with Renzo Piano.

[38] Cardiff Council granted planning permission for the building on 8 November 1999, and by 26 January 2000 the National Assembly voted to progress the project to the next stage.

[39] The review was carried out by the Assembly's Management Services Division, the Property Advisors to the Civil Estate and Symonds Group Ltd.

[51] Edwina Hart AM, the Minister for Finance, Local Government and Communities, approved the final project design on 18 January 2001 and by 1 March 2001, the groundbreaking ceremony took place to mark the beginning of construction.

[2] Six months after construction had begun and with only the piling and a temporary road around the site having been completed,[48][52] Hart announced on 17 July 2001 that the National Assembly had terminated the contract of RRP.

[61] The cowl sits 6 metres (20 ft) above the roof line and rotates when the wind changes direction to ventilate the debating chamber.

[66] The 5,308 m2 (57,130 sq ft) Senedd building was opened by Queen Elizabeth II, the Duke of Edinburgh, the Prince of Wales and the Duchess of Cornwall on 1 March 2006 (St. David's Day).

[68] Addresses were later given by John Price MP, the Deputy Speaker of the New South Wales Legislative Assembly, Morgan and Elis-Thomas.

[68] A set of commemorative envelopes and postmarks were issued by the Royal Mail to mark the opening of the Senedd building, in the form of a souvenir sheet.

[70] The breach contributed to the death of John Walsh, a foreman working for Ferson Construction Services Ltd, a subcontractor of Taylor Woodrow.

The accident occurred on 14 March 2004 and was due to a cavity wall that Mr Walsh was filling, collapsing on him, even though Taylor Woodrow Construction had recognised the risks before the contract had begun.

In a report published in March 2008 by the Wales Audit Office, the reason for the increase was that the original estimate of £12 million was not based on any detailed design of the final requirements of the building.

A spokesman for the National Assembly said, "The repair figures are not excessive for a public building that has hundreds of thousands of visitors each year.

[78][79] On 26 June 2008, the Prince of Wales officially opened Siambr Hywel, the then National Assembly's youth debating chamber and education centre.

[86] In 2008, Elis-Thomas announced that the Pierhead Building would display the history of the Black community in Butetown, Cardiff Docks and Welsh devolution.