Yesterday, I hosted a Green Property Summit for the Property Council, which brought together a 'who's who' of our big commercial developers, all of them looking at what our cities should look like in future. 

And by "future," we're talking 2020. So, soon.

The summit brought in some really interesting speakers from all over the world: the United States, Australia, Singapore, and here.

The Americans talked about what they’re doing in Manhattan to hit the so-called triple bottom line -- an environmental, sustainable, and economical city. We saw images of a mixed-use mini city they’ve built there. The philosophy behind this vast development is "live, work, play." You can do all three in this intensified housing, commercial, and recreational development. And the mini-city has been built on these huge plates - almost a shelf, if you like - that sits above a subterranean train station so your transport links are below you.

And sure, New Zealand is a lot different to Manhattan, but in countries like the US and Singapore, they've had no option but to go up and they've done it well. The Australians are doing it well too. Some of the developments in Melbourne and Sydney are magnificent. Big, bright, light apartments with access to everything you need nearby, and large, beautifully developed green areas outside.

And yet here, we almost break out in hives when we think about apartment living. We automatically think of life in a small dark shoebox. The Americans said their advice to our major cities was to rethink what we're doing. To stop the sprawl and to build up, but to build up well with top quality housing.

And it was the same advice from the boss of Singapore's building and construction authority who spoke about how in there, they had to take a country that's about three-quarters the size of Auckland, and house 5.6 million people. They had to build well and with an over-arching philosophy that created enough space, light and outdoor living for everyone. Again, that same approach of live, work, play.

We are doing it here too. Have a look at some of the magical commercial architecture in Christchurch and in Auckland, in some of the developments in Britomart, the Wynyard Quarter, and the Viaduct. Clean buildings. Sustainable. Full of light, good air, and space.

And why is this important? Well, in three years, 5.1 billion people will call the world's cities, home. And while that's just fine if you live in London or New York or Sydney, our cities could function better. By better, I mean with more intensified housing that create not just liveable communities, but communities with good social and health outcomes too.

I've been guilty of being wary of high-density housing, but at yesterday's summit and looking at what's going on around the world, I saw the situation in a new light.

It makes sense to stop sprawling and to build up, but not in isolation. Done well and done right, we can create thriving communities within our cities.

We just need to stop thinking that housing begins and ends with a quarter-acre section.