The Senedd has been hosting assembly debates for two years
The Welsh Assembly's new home was built broadly on time, on budget, and reached the highest environmental standards, a financial watchdog has concluded.
But a six month delay in the completion of the building, the Senedd, led to additional costs of £794,000, according to the Wales Audit Office (WAO) report.
Increased construction costs and a big rise in information and communication technology (ICT) has been blamed.
The total final budget for the Senedd increased from £66m to £70m.
Despite savings in a number of areas within the project, there was an extra £2.6m for security measures, an extra £2.8m for works at the rear of the building, and £1.8m on other external works.
The cost of ICT and broadcasting equipment also increased from £6.7m to £8.2m.
Auditor General Jeremy Colman said the project was a "success story".
"The second phase of the project to build the Senedd clearly benefited from lessons learned in the first," he said.
"New processes, tighter financial forecasting and better project management resulted in the successful delivery of the national assembly's Cardiff headquarters.
"I hope my recommendations will ensure that these important lessons will influence future similar projects," Mr Colman added.
The report also notes that an overlap between construction work and the installation of ICT equipment meant that dust caused by construction works caused damage estimated to be between £10,000 and £12,000.
The document states that problems such as a leaking roof and leaching of salt on the steps in front of the building did not result in extra costs.
This was because the building contract included a 12-month defects liability period, which has since been extended, and "appropriate levels of retention monies have been withheld until those defects are resolved" according to the report.
The Senedd was specifically designed to be an "exemplar" of "sustainable construction" operating to the highest environmental standards.
It was designed to have high environmental operating standards
But the WAO report notes that electricity costs have exceeded original estimates by as much as 50% due, in part at least, to the building being open to the public for seven rather than five days a week.
The report concludes that the project was handled well by the Welsh Assembly Government and that around £16m of the total construction price was spent on Welsh services, labour and materials.
The final cost of the project was £70m - £4m more than the previous revised estimate of £66m.
But the report recommended more detailed specifications be made for any future major projects and that the assembly government "formalise" any lessons learnt.
It also calls for the Assembly Commission, the body which manages the Senedd, to produce regular reports on the building's performance.
Commission Chair and Presiding Officer Lord Dafydd Elis-Thomas said he was delighted with the report.
"This was an excellent project which led to an iconic building of architectural significance that everyone in Wales can be proud of," he said.
"We have a wonderful building designed to the very highest environmental standards, and it is essential that we ensure these high standards are met," Lord Elis-Thomas added.