It was great to see a bevy of global architects converge in Sydney this week.

One lot was Richard Rogers and Ivan Harbour from Rogers Stirk Harbour + Partners in town to check on the almost complete Barangaroo towers the pair’s firm had designed, and to address the NSW Property Council’s Breakfast with the Architects event on Wednesday morning in Tower 3 of the project.

Rogers was pleasingly focused on sustainable cities. Always a good message to have reinforced whenever possible from famous visiting people (in case we don’t trust our own judgement).

Get away from car dependence, Rogers said, build within the city boundaries, intensify wherever you are, amidst the community and infrastructure that gives you the activation that makes cities great. Among the slides he showed was a powerful comparison of Barcelona and Atlanta. Same population, roughly, but vastly different land areas and carbon emissions.

London’s plan was to retrofit its 600 neighbourhoods before it started sprawling outside the boundaries, he said

“Don’t build outside [the city borders]; it’s not good in terms of friendship and it’s certainly not good in terms of climate change.”

The car was good in some respects, Rogers said, but it could also carry the blame for much damage.

He showed bucolic images of European “Renaissance cities” with clear demarcation between the town and the countryside.

We need to respect those boundaries today, he said.

In the South of France urban sprawl had been a destructive force, environmentally and socially.

“Once have sprawl you don’t have the integration of the neighbourhood. You don’t meet your neighbours. You get into your car and go to work,” he said.

“People don’t go to suburbia for fun.”

There is a big cost to suburbia, he said, particularly in energy and climate change.

“Climate change is probably the most dangerous thing we’re facing globally.”

The City was not amused

But after such worthwhile and positive advice in the morning, Rogers reportedly proceeded later in the day to rub the social sustainability sentiments espoused by the City of Sydney up the wrong way. Big towers right on the water’s edge was a fine thing to do, he said. Harbour agreed, saying it meant the towers could “open their arms to Pyrmont” (albeit across the water).

Not according to the City, which slapped down the idea in Fairfax Media and would have demanded a quite different outcome at Barangaroo, it claims, if the state government had not wrested development control from its arms. The harbour should be reserved for the community, it said.

Rogers and Harbour were not the only glittering architectural gurus in town.

An even bigger day for architects was scheduled for Thursday, which marked the conclusion of a competition for another new tower, at Circular Quay also by Lendlease, and over which compatriots Foster + Partners and David Chipperfield Architects plus US’s Skidmore, Owings & Merrill, Kohn Pedersen Fox Associates and HOK, are all lining up against locals BVN and Hassell for the job.

Some Australian studios are also teaming up with foreign talent on the competition: Fender Katsilidis Architects with Skidmore, Owings & Merrill; Allen Jack and Cottier, with Kohn Pedersen Fox; PTW with HOK; and Architectus with Foster + Partners.