The boss of Auckland's City Rail Link has ruled out giving the public another chance to walk through the first section of the rail tunnels.
However, officials have confirmed other sections of the project will be opened to the public over the next five years, after being "blown away" by interest in the first open day event.
Ten thousand people were given rare access the tunnels between Britomart and Albert St during Sunday's eight-hour open day event.
Almost 100,000 more tried to access the ticket website during that period but missed out due to unprecedented demand.
City Rail Link chief executive Sean Sweeney said construction work had to be paused for today's event. He confirmed the next time the public are inside that section of tunnels will be on a train.
"We were blown away [by the demand for tickets]. We were hoping people in Auckland would be interested, but we never thought it would be quite that level."
Sweeney said people who missed out the first open day will be able to attend open days for other sections of the tunnel, as they are completed.
"We're looking at what else we can do. It's five years until completion.
"People need to have a chance to have understand what we're doing and engage with it. They're paying for it. We're going to do things like this all the way through."
Denise Collins was among the first through the tunnels this morning.
"I went to the walk on the Harbour Bridge in 1959, then we did the Waterview Tunnel with our grand-kids, and now they're doing it now," she said.
Collins said it was sad it had taken this long to realise Sir Dove-Myer Robinson's rapid rail plan, but she was glad the project was finally being done.
Jack Clark had also waited years to see the tunnels built, but said he was very happy with what he saw at today's open day.
"I am pleased to see it in action. I wish it had happened when Dove-Myer was here, and it would have cost us far less.
"However, I was surprised by how far they'd got, and the workmanship was immaculate."
Transport minister Phil Twyford said he had advocated for the project for years, and the level of interest in today's open day showed the general public supports it too.
"We made the arguments for the City Rail Link. We won the argument that we needed to make this invest and turn Auckland into a truly modern city. We've got to keep going.
"Make no mistake about it - this project is transformational for Auckland and it's just the latest of a series of infrastructure projects we're going to make to get Auckland moving."
Sweeney said contractors are now moving on to demolition work at upper Albert Street, K Rd and Mt Eden.
"They'll start building stations at those three locations. There's also a massive excavation happening at Mt Eden to launch the tunnel-boring machines in a year and a half.
"These are very big complex projects, and unforeseen things happen all the way through.
"We're tracking well at the moment and we'll continue to monitor it."