The Prime Minister yesterday took a tour around a busy railway station which doesn't yet exist.
Mr Key slipped on a virtual reality headset for a walk around Aotea Station - one of the proposed underground stops for Auckland's $2.5 billion City Rail Link.
The station is projected to handle around 12,000 people in peak hours and be one of the busiest hubs on the network.
Describing the visit to a downtown control room as a chance to grasp the complexity and potential of a crucial venture, Mr Key stressed the importance of making sure one of the biggest engineering missions in Kiwi history gets a "successful execution".
"This is something that's been talked about for decades. It's exciting, but something you've got to get right," Mr Key told the Weekend Herald. "The successful execution of the plan will allow it to be delivered on the broad budget of $2.5 billion to $3 billion.
If you don't do that, everyone can see how challenging that might be.
"There's also a lot of commercial investors [that] need to have the confidence that the plan can be well executed, is well thought through and can be what Aucklanders want.
"It's the first opportunity to really see the team that they've put together. This is a substantial redevelopment of the Auckland landscape, particularly the CBD. You're retro-fitting an enormous piece of infrastructure."
With Civil Defence, Youth and ACC Minister Nikki Kaye, the Prime Minister was shown early developments in Auckland's underground system pegged for completion in 2023.
A number of issues are still to be ironed out at the Government's negotiating table, including the biggest question of how the $2.5 billion budget will be paid.
The council hopes the Government will stump up half the $2.5 billion cost, but a decision is still pending. Mr Key says a deal should be hammered out on how the bill will be split over the next 10 months.