Auckland's former Chief Post Office reopens to the public this afternoon after four years in which two new tunnels were built under the 109-year-old heritage-listed building.
From 1pm, people will again be able to get inside the CPO or Britomart facing the newly refurbished public square, Te Komititanga, which means to mix or to merge in te reo Māori.
The old building between Quay St and Customs St has been shut since 2017 so work could be carried out creating the first or CBD stage of the $4.4 billion City Rail Link beneath.
The Britomart train station has remained open during the work but could not be accessed via the CPO until today.
New twin-tunnel connections are under construction from Britomart to Mt Eden in that project due to be finished by 2024 but work is now concentrated to the west at the Mt Eden, Karangahape and Aotea Station ends of that job.
The new tunnel boring machine will in a few weeks begin spinning to build the first tunnel from Mt Eden in that project by the Link Alliance, whose project director is Francois Dudouit.
CRL today called the heritage building work a "complex engineering feat to remove original support columns out of the way of the CRL tunnels and transferring the CPO's weight to new foundations without damaging the Category A-listed heritage building".
Auckland mayor Phil Goff, CRL chief executive Sean Sweeney and Transport Minister Michael Wood attended this morning's event to celebrate the reopening, after karakia from Tāmaki Makaurau tangata whenua.
Sweeney said the ground floor of the CPO had again become the main entrance to the Britomart station with ticketing and information facilities, access to Britomart's adjoining train platforms, and shops.
Mark Lambert, Auckland Transport's executive general manager of integrated networks, said up to 38,000 people use Britomart Station daily.
AT is now restoring and repairing the CPO's facade.
One of the first CRL contracts taken was to convert Britomart from a dead-end to through station.
"What followed was some astonishing engineering to overcome challenges to build the tunnels: working in confined spaces, dealing with some pretty sticky reclaimed land at the bottom end of town, protecting a building with a top heritage rating weighing 14,000 tonnes while we transferred its weight safely and carefully on to new foundations, and keeping Britomart Station next door open and operational all the time," Sweeney said.
Machinery was specially modified to be used under the CPO.
The stone building was supported on high-strength steel made in New Zealand.
CRL worked with contractors Downer NZ and Soletanche Bachy JV, Heritage NZ, Auckland Council and Auckland Transport.
The main entrance to the building is now once again from the public square, now with the new kupu Te Komititanga.
Work on the facade is continuing, along with construction around the CPO in adjoining Galway St and Tyler St.
The new tunnels now run under the renamed Te Komititanga, beneath the new $1b Commercial Bay and up Albert St as far as Wyndham St.
Construction of the tunnels, together with two new underground stations, is under way by the Link Alliance from that point to Mt Eden.
A completed CRL will enable longer trains, from six to nine cars. Services will also be more frequent and faster, CRL said today.