Eyesore, ghetto, jungle, goldmine, little United Nations. These are all words that have been used to describe Chungking Mansions, a building complex that is seen as both a foreign island in Hong Kong and an important part of the Chinese city's identity.

From the outside, Chungking Mansions looks like a single, imposing concrete block - 15 identical residential floors on top of a neon-lit, two-storey mall.

Past the front, it is like a maze - there are in fact five separate blocks, 10 lifts and multiple old, twisting stairwells filled with swathes of electrical cable, crumbling concrete and graffiti in multiple languages.

The complex began life as an upmarket residential estate in the 1960s, but has since become a hub for traders from developing countries, backpackers and asylum seekers in Hong Kong.

More than 10,000 people are estimated to enter or exit the building every day, and African and South Asian faces often outnumber Chinese faces - something remarkable in a city where 94% of residents are ethnic Chinese.

The building complex has a somewhat notorious reputation among locals and, until recently, many in Hong Kong were wary of stepping inside.

However, the building has a buzz that most Hong Kong Chinese would also recognise - nearly everyone is there to make money.

'Low-end globalisation'

Entering the building, touts try to lure the visitor to their restaurant, or offer a hotel room.

Image caption Chungking Mansions consists of five 17-storey buildings. Image caption It is home to hundreds of small businesses Image caption Isolated corridors and stairwells connect different parts of the building complex Image caption Its hundreds of CCTV cameras are monitored constantly Image caption The building has become increasingly accepted by local Hong Kong residents previous slide next slide

Across the first and second floors are shops selling clothes, computers and boxes of cheap electronics such as mobile phones. As well as selling to the public, the stalls cater to wholesalers who ship goods to Africa and South Asia.

Gordon Mathews, an anthropology professor at the Chinese University of Hong Kong who spent four years researching and staying in Chungking Mansions, describes the complex as "a world hub of low-end globalisation".

Dennis Cheung I'm a resident of Chungking Mansions. I've lived here for more than 20 years, since I was small. When I was small, my friends would ask me: "How can you grow up in such a building?" But as local residents we know that the building isn't so dangerous. When I was small there were fires about once every two months. We would have to evacuate during the night when the alarm rang. Most of the time they were just small fires. What we were most worried about was the blackouts. The most serious power cut was in 1993. All the elevators and water pumps stopped for a week. I had to walk up 10 floors every day when I came back home from school, and carry buckets of water up to our flat. I think it's quite a special experience growing up here - you can't find another place in Hong Kong where you can grow up with people from so many different backgrounds.

Traders from developing countries come to Chungking Mansions to buy goods in demand back home, he says, "carrying their goods in their own luggage, or renting a container or part of a container, and shipping the goods pretty much on their own".

The deals are done "on the basis of trust, and often under the radar of the law," he says.

Many traders try to avoid import taxes by carrying their merchandise themselves or bribing customs officials, while many of the employees in the shops are working illegally.

Prof Mathews estimates that in 2008, about 20% of mobile phones in use in sub-Saharan Africa had been sold in Chungking Mansions, although that number has since decreased.

Many of the phones sold today are 14-day phones: phones which were returned by European customers within 14 days of purchase, which retailers buy at a discount and sell on.

Directly above the phone shops, a very different kind of business is thriving.

The 15 storeys above the mall are packed with guest houses converted from the building's original residential apartments.

Numbers of visitors have soared in recent years, as relaxed border controls have led to an influx of tourists from mainland China.

Lam Wai-lung owns the Dragon Inn, one of the larger guest houses.

The smallest room has barely any space apart from the bed and costs HK$180 ($23; £15) a night, while the largest - the deluxe honeymoon suite - costs $700 ($90; £60) a night during peak season.

Image caption Ms Lam says media coverage of Chungking Mansions has improved

"A few years ago, 70% of my clients were from Japan," she said. "Now, around 70% of the customers are from mainland China, as they have become wealthy."

But China's opening up has also presented threats to businesses in the complex, as some mobile phone buyers now head to Guangzhou instead of Hong Kong, traders say.

Eddie Wong, a wholesale phone dealer from Hong Kong, said competition from China was fierce.

"Business isn't as busy as before. China has opened its markets and traders can apply for visas [to mainland China] very easily. Meanwhile, the Hong Kong government has tightened visa requirements for African customers, so most of them go to China now."

Joe I work as a trader in Chungking Mansions. I'm from India, but I've been in and out of Hong Kong more than 100 times in the last 12 years. I come to Hong Kong for business - ordering clothing, electronics, cosmetics and whatever else is in demand in India. Often, people help me buy things from China and send them to Hong Kong. I then arrange for them to be hand carried to India - it's more convenient transporting goods in your hand luggage than in cargo containers - customs are less likely to check your carry-on bags. I came to Hong Kong to make money. Twelve years ago, it was difficult to make money in India, business was slow. In Hong Kong, it's hard, but at least it's possible. You can even make money by helping shops check second-hand mobile phones [to make sure they work] - you can make around HK$1 ($0.13; £0.08) for each phone you check.

"Also, they can buy phones more cheaply in China."

Many traders were reluctant to be interviewed. Some were asylum seekers and illegal workers who could not risk being identified - while others were simply busy making money.

One man said he had been in Hong Kong for over five years. While his asylum application was being processed, he was working illegally to support his family.

Illegal workers are a key part of Chungking Mansion's business model, Prof Mathews says.

"If you pay workers [the minimum wage] here, prices would have to go up and all of the developing world traders would not be able to afford the goods here," he said.

"[While] it is illegal, in my experience the police don't tend to act on it much, because it's hard to catch someone working illegally, and these are jobs that locals won't do."

Constant surveillance

With its five separate blocks, winding staircases and constant flow of people, Chungking Mansions may seem like a good place for those who want to disappear off the radar.

But in fact, comprehensive CCTV coverage makes it nearly impossible to enter or exit the estate undetected. When I approached the management office for an interview, they said their security staff had noticed me hours ago, after my loitering drew their attention.

The first CCTV cameras were installed around 10 years ago in a bid to improve safety, security manager Matthew Tsoi said.

Image caption The management describes 'cultural differences' as one of its largest challenges

There are around 330 CCTV cameras now, covering around 70% of the building's public spaces.

The management office takes obvious pride in its CCTV system, and the role it has played in improving security.

Crimes still take place - the reported rape of a mainland tourist in June sparked headlines. But an arrest was made hours after the crime was reported to police, as officers used CCTV footage and door-to-door searches to apprehend the suspect.

The management office appears to take a pragmatic approach to the illegal workers in the building.

"Of course we assist the police if they ask for CCTV footage or other information, but to be frank illegal workers don't create many problems for us from a management perspective, unless they commit crimes or are disorderly," Mr Tsoi said.

Parminder Preet I came to Hong Kong in 2004 and started an Indian vegetarian restaurant, Smrat Pure Veg, with my husband. It was difficult starting out because most people in Hong Kong are non-vegetarian. But business is OK now. I feel we are lucky to be vegetarians, because new viruses come along every year, like bird flu - so I think we are safe! We started in Chungking Mansions because it's the main area for Indian business people. We also have employees that help us look for customers. The first time I came, I felt scared! There were lots of different people. In India, I didn't see so many people from Africa or Pakistan. But after I was here for a few months, I felt I knew how manage. Now, I feel that all people are good.

A greater challenge was managing cultural differences between the thousands of people in the building, he said.

"For example, some Indian families may burn incense 24 hours a day, and their neighbours may not like the smell. Or there are Muslims who need to pray facing a certain direction each day, who will leave their prayer mats out in public areas."

"Most buildings in Hong Kong are quite homogenous, with mostly Cantonese people, so there aren't as many different cultural activities or living habits that need to be accommodated," he said.

Despite this, the different ethnic groups in Chungking Mansions appear to get on relatively well. "The world seems to become smaller in Chungking Mansions," dealer Eddie Wong said.

"Even though there are so many people from different races and religions, they all know what they're doing in Hong Kong... most have come here to make money. So that's why they will not have major conflicts - even Pakistanis and Indians are friends here."

Chungking Mansions' reputation amongst local people has also improved over the years.

"Generally, before, any Hong Kong Chinese coming to the building would be frightened, and would go straight to one of the upstairs restaurants," Prof Matthews said. "Today, a lot more Hong Kong Chinese are coming in, hanging out and taking a tour of the building."

This is in part due to positive press coverage and in part due to greater tolerance of other cultures among young people.

A third reason, Prof Mathews said, was that Chungking Mansions was increasingly accepted as part of Hong Kong's identity, as the city seeks to define its relationship with mainland China and the rest of the world.

"Underlying all this, I think Hong Kongers want to see Hong Kong not as Chinese, but as increasingly international," he said.

"Chungking Mansions is seen as proof of Hong Kong's international nature. It's one reason why the place has become quite popular with locals."