Wellington Mayor Kerry Prendergast says cost overruns at a wildlife centre in the city were unavoidable and extra money was justified.
She says an upgraded centre will now reopen in May.
Doing up Zealandia, formerly known as the Karori Sanctuary, was expected to cost $14 million but it will now cost almost $17 million.
Ms Prendergast says an extra $2.3 million was voted for the project in a hearing behind closed doors around a year ago.
She says the vote was confidential for contractual reasons, but made real sense to safeguard the upgrade of a vital piece of Wellington heritage, and the council was left with little choice.
Ms Prendergast says the council had some concerns about the centre and required a new board to be installed as a condition of paying extra money.
She says the Government was also contributing money, but this was conditional on a contribution from the council.