The port has to move but there's nowhere for it to go. That's the problem facing Auckland as it inches towards a decision on the long-term future of its container port, the car imports, the cruise ships and the land they all currently take up on the edge of the sparkling Waitemata harbour.

It's an unsolvable problem that has to be solved. We need a port and we need it to stay highly functional. And the land it sits on now is both publicly owned and the most valuable real estate in the country – we have the chance to create something very special there.

On Tuesday this week the Herald published a proposal by the architectural firm Archimedia for transforming the land. New beaches, a lagoon, a "volcano", a Maori cultural centre, hospitality, apartments and offices all featured.

The proposal excited a lot of interest among our readers. The prospect of swimming and other calm-water recreation so close to the city has been especially popular. So have the big new parklands and the 8.2km of boardwalks and other public walkways/cycleways offered by the proposal.

READ MORE: Andrew Dickens: Short term focus means we can't have great things

We've also heard concerns. Some ask why commercial development will be allowed on the site. Others want to know where the port will go.

The value of commercial activity is clear enough. Apartments to house 8000 people will help provide population density, giving life to the precinct. The land would be made leasehold, not freehold, and commercial developments will pay for public amenities.

Will that mean a new wall of buildings to block the views? The answer depends entirely on the final designs and the consenting process. It doesn't have to be a problem.

The question of where the port will go is far from settled. But whether it has to shift has already been resolved. It's worth remembering how that happened.

In 2015 then-mayor Len Brown set up a Port Future Study with a Consensus Working Group. The Chamber of Commerce and the Employers and Manufacturers Association were involved, along with Generation Zero and Urban Auckland, Ngati Whatua and the Tamaki Alliance, property developers, resource management experts, shipping, freight and logistics companies, and Ports of Auckland Ltd itself. It was a high-powered, diverse and very representative group.

A year later, in July 2016, they reached a remarkable consensus. The group agreed:

• The existing port is not big enough for the freight and cruise demands it will face in 25 to 40 years. (The port handles close to one million containers a year now; that's expected to rise by a further million every 20 years.)
• Rail and road links out of the port will reach capacity within the same period, if not earlier.
• Over the next 20 or so years the port will require extra capacity on its existing site, "prior to a new port being established".
• Economic, environmental, cultural and social factors are all critical in deciding the future of the port and of the port land.
• It is in Auckland's best interests to keep all the existing functions of the port. So, for example, the city would lose out if car imports were shifted to Northport, near Whangarei.
• Other North Island ports will lack the long-term capacity to take over entirely from the Auckland port.
• Taking all this into account, there is "sufficient probability" that a new port for freight will be required. Planning should proceed on that basis.
• Berths for cruise ships should be retained in the city centre.

A long list of 28 site options was identified, including Northport and Tauranga. That was narrowed to eight and then finally to two: the Firth of Thames and the Manukau Harbour.

The hope was that all these conclusions would become the foundation for debate and planning about the future of the port.

Since then, the Government has changed and the coalition agreement between Labour and New Zealand First commits them to a ports future study of their own. The details of that are soon to be announced.

NZ First campaigned in the election for the car import business to be relocated to Northport, and other functions to be dispersed to the regions too. However, Infrastructure Minister Shane Jones told the Herald this week that the chief executive of Ports of Auckland and others had been briefing him and what they said had "taken my fancy".

Shifting the port is not an easy proposition, Jones said, and he understood that much better now.

Why the Firth of Thames or Manukau Harbour? The first part of the answer is that the most important site is not either of those, or the current Waitemata site. It's Wiri.

That's where Ports of Auckland has its the inland port, where much of the freight is taken for sorting and dispatch. Wiri is the fast-growing heart of freight logistics in the upper North Island.

The Manukau Harbour is a very short hop, across largely open land, to Wiri. The Firth of Thames would also be relatively easy to connect to Wiri, with a dedicated road and rail corridor through the Hunua Ranges. Both options would allow freight capacity to grow without the transport links disrupting commuter traffic.

A port in the Firth of Thames would be on a new island connected by a causeway. There are many breeding grounds for birds in the area but, surprisingly, around the world port activity has not been disruptive to bird breeding.

A port in the Manukau would require extensive dredging, and shipping would be subject to the wilder conditions of the west coast and the Manukau Harbour entrance.

There are many other environmental, cultural and social issues to be considered. The cost of shifting the port was identified by the Port Future Study as being $5 billion, although there are other analysts who dispute this.

Meanwhile, this week the Auckland Council received an officials' report on Ports of Auckland's own 30-year plan. It includes the complete demolition of Marsden Wharf, a building for handling car imports, a hotel and a further extension of Bledisloe Wharf into the harbour.

That extension was to be 40m, but Ports of Auckland has scaled it back to 13m.

Mayor Phil Goff said he didn't know if the hotel was a good idea or not, but noted that Ports of Auckland didn't need a decision on it for five to 10 years. He also said he was "frankly uncomfortable even with the 13m extension" but was not going to oppose it.

Lindsay Mackie and Sean Park of Archimedia presented their plan at the same meeting. Goff was enthusiastic, calling it "a great design" and "a great first step".

Planning committee chair Chris Darby was also keen. He called it "extremely stimulating" and said it was a reminder to council not to let Ports of Auckland do anything that would compromise the longer-term potential of the site.

He was particularly worried about that Ports of Auckland proposal for a hotel.

Goff's main message to councillors, in regard to both the Ports of Auckland plan and the Archimedia plan, was that they needed a bigger picture. "Look at South Bank in Brisbane," he told his colleagues. "It used to be a decrepit port area. Look at Darling Harbour in Sydney. We could do the same in Auckland."

He reminded councillors that Ports of Auckland, as part of the Port Future Study, had accepted it would outgrow its site. "They knew that in 30 years they'd be out of there," he said, adding that this was "confirmed in a workshop" the council held a couple of weeks ago.

He didn't think either Northport or Tauranga would provide a solution for Auckland. He said it was a "no brainer" to support the Government as it considered its options for guaranteeing supply chains in the upper North Island. It was also a "no brainer" for Auckland "to protect our interests and our dividends".

"It's our port, not the Government's port," he said.

The mayor, and in all likelihood Auckland Council with him, want to shift the port but not by way of losing the car importing or any other functions. There's a battle with the Government brewing on that one.

As for the Archimedia plan, it's not a blueprint. Lindsay Mackie calls it a conversation starter.

Archimedia has left it to the economics and environmentalists and politicians and others to worry away about when and where to shift the port. But while that happens, it wants to inject some imaginative thinking into the debate about the current site.

It wants to lift the debate above the short-term distractions of new hotels and 13m reclamations and focus instead on big-picture planning and long-term opportunities.

It has challenged Auckland to think about what we would really like to see on our downtown waterfront.