By Vaudine England
BBC News, Hong Kong
Hong Kong may seem crowded enough to the seven million people who live in small flats in high-rise neighbourhoods.
Some fear Hong Kong's status as an independent city will be harmed
But government-backed planners say the city's future lies in numbers, big numbers.
They say Hong Kong should be merged with Shenzhen, the southern Chinese city across the border, to make a mega-city of 20 million people.
Only then can Hong Kong be one of the world's great cities, argues a research report by the government-linked Bauhinia Foundation.
"It is not only merging, it is really creating a metropolis between Hong Kong and Shenzhen," Anthony Wu, director of the Bauhinia Foundation, said.
"If you look at the long term competitiveness of Hong Kong, Hong Kong has only got seven million people, and... Shenzhen has 13 million people. You need to merge the two to create a bigger metropolis to take advantage of China and the world."
So does he envisage an endless sprawl of buildings and highways to gobble up all the space and greenery between urban Hong Kong and southern China?
Mr Wu says the first goal is to build a direct express train link between the two cities' international airports.
The next goal would be to ease visa procedures for residents of Shenzhen to come into Hong Kong more readily.
At present, Hong Kong people can move in and out of China on a thumb-print if they have their permanent residency smart card.
Mainland Chinese must apply in advance for visitor permits, and can only get two at a time. They cannot wake up in the morning and decide to pop across to Hong Kong for some business without planning ahead.
More controversial is the Lok Ma Chau Loop - one of those quirks of history which may have huge repercussions.
Back when Hong Kong was a British colony, its border with China was marked by the Shenzhen River, and like many rivers, it curved.
Links between Shenzhen and Hong Kong have grown in recent years
When the river was straightened, it left a square kilometre of land, technically owned by China and now under Hong Kong rule, known as the Lok Ma Chau Loop.
"Hong Kong and Shenzhen have been arguing about this, who should do what, so we're suggesting, in this place here, the land-right belongs to Shenzhen, but the administrative rights are Hong Kong's," Mr Wu said.
"So if we could use this as an example, as a pilot, Shenzhen people could just go there without visas, Hong Kong people could just go there, and let the market decide.
"Maybe this is a very good place for health care... for high-tech factories... for museums and whatever. This could be an example where the mainland and Hong Kong actually work together, borderless."
It sounds exciting, particularly for those Chinese local government officials who stand to make a fortune if the Loop is developed, Hong Kong's leading business commentator, Jake van der Kamp, says.
"They would stand to make a lot of money. At the moment they can't develop it because it has got no water, no sewer, and lots of contaminated mud that can't be dug out because the Mai Po nature reserve is just down the stream," he says.
"And they've been, for the last 10 years, trying to get it developed and sold and make a lot of money. They haven't been able to do it yet and I think this whole idea of a megapolis is in fact a red herring to try to get the Lok Ma Chau loop developed."
But what of the larger idea. Does a bigger population make a greater city?
Mr Wu, whose research report was promptly followed by a seminar hosted by the government's Central Policy Unit backing the same idea, says yes.
"If you look at London, New York [and] Tokyo, all these major metropolises, first of all you do need a big population," he says.
Put it to him that what makes cities great is culture, history, traditions and values more than mere numbers of people, and Mr Wu barely rests for breath.
That is why Hong Kong should merge with China, he argues, as Hong Kong has the legal system and China the 5,000 years of culture.
The local establishment newspaper, the English-language South China Morning Post, seemed to support this all the way.
An editorial argued that the "one country, two systems" mantra, designed to guarantee Hong Kong's autonomy under Chinese rule, was a "straitjacket", which "but for history" was holding Hong Kong back.
This barrage of big ideas has left not a few Hong Kong people breathless, but in a different way to Mr Wu.
No sooner has the idea of merger arisen, than it seems to have become a political re-arrangement, in which Hong Kong risks losing its status as an independent international city and becoming just another bit of China.
The implications of that worries those concerned about Hong Kong's other freedoms - of press, of assembly and of ideas.
"What is required for a merger? This place is already merged," Mr van de Kamp says.
"Hong Kong provides the services to the whole Pearl River Delta that provides manufacturing and cheap wages and together they put junk Christmas toys into the United States."
He went on: "There are too many government officials in Hong Kong who believe it their duty to please the authorities in the mainland and because the ones in Shenzhen and Guangzhou are nearer than the ones in Beijing, those are the ones they please."
It is left to a population geographer, Professor Jianfa Shen at Hong Kong's Chinese University, to bring the grand plans back to earth. He says the key is to allow those who want to move across the border more freely, to do so.
But, he says, the two cities have different wish-lists and finding a consensus will not be easy.
Hong Kong wants the airports connected, a clear division of labour, co-ordination so that the ports do not compete, better environmental measures and more investment.
Shenzhen, he says, wants easier travel arrangements into Hong Kong for its people, and more co-operation of scientific research.
"Recently, yes, the two governments have become much more interested in how we can do something together," said Professor Shen. "But it will never become a single city, it's not possible."