The National Crisis Management Centre in the basement of the Beehive, also known as the Bunker, was activated today for a major civil defence exercise. RNZ went inside to have a look.
Today's exercise was the first day of three over the next month, testing the country's readiness for a major tsunami.
The heavy door to the bunker is painted an anonymous grey with no signage. But once inside and down the stairs, the bunker opens out into a series of rooms coming off a central core, with one large control room.
In the control room, there are about 50 people seated at series of work stations.
One wall of the room is completely covered in big screens showing graphs, maps and incoming data.
Today's exercise was based on the scenario of a tsunami generated by an earthquake in the Kermadec Trench taking less than three hours to reach New Zealand.
At one workstation, officials collated information coming in from tide stations around the country, to figure out where and when the tsunami would hit the coastline.
Other stations coordinated emergency responses in the regions and liaised with various agencies, including the police, Defence Force and Ministry of Foreign Affairs and Trade.
Ministry of Civil Defence director Sarah Stuart-Black said the exercise was a real test.
"We actually went to GNS to provide us with a realistic scenario for this exercise is to make sure that it was being tested for real, rather than something that was just a pick out of the sky as it were.
"What we've found is that it is playing out as expected, which is terrific."
Ms Stuart-Black said officials knew there was an exercise today, but nothing more than that.
"So until the scenario kicked off nobody knew, other than the fact that it was going to be tsunami, what was involved.
"It's actually testing the callout procedures, the coming down and identifying what are the priorities, what do we need to be focussed on.
"So you're playing it cold, but with the fact that you are testing all of those arrangements that have been worked through, where there's been training for agencies involved to see 'all right how does it work in practice' and what we're seeing is - it's working very well."