Sonagachi, India - The entrance to one of Asia's largest red-light districts is filled with hordes of young men washing themselves at water taps on the roadside.

They stare as 39-year-old Geetha Das, sporting kohl-lined eyes, strides by purposefully - but she barely glances at these pimps and middlemen.

"I am a sex worker," Das said. "Just like others are engineers and doctors and pilots, my job is to give sexual pleasure."

Das has been a resident of Sonagachi, which is home to about 7,000 sex workers, since 1992. She was 16 years old at the time.

Born in India's eastern state of Bengal, in an impoverished area known as North 24 Parganas, Das was married off at age 12 to a 37-year-old man. His abusive and violent behaviour caused Das to return to her parents' home, along with her two children.

Poverty and hunger forced Das to head to the bustling metropolis of Kolkata in search of a job. A friend brought her to Sonagachi - a move that, she said, secured her children's future.

"Both my children have completed their education and are working now," said Das.

"Would I have been able to pay for their studies if I had stayed at home? Society should first look at itself before condemning us… Did anyone give us a good job? Society has failed people like me," Das said.

Das explained that for her, self-respect is everything - a curious term considering that sex workers in India are ostracised from mainstream society.

"We sex workers in Sonagachi do not have anyone to support us - what do we do if our husbands leave us? Most of us have no education and two to three kids. Yes, we can work as domestic help to support our families. But even then men force themselves onto us. Money is the only thing that assures self-respect in society," Das said.

'Money and excitement'

One woman who did not want to use her real name in order to protect her identity, said money was a big lure for her, but she said the thrill of the chase was even more fascinating.

"I like to have adventurous sex with different men," she chuckled. She has a husband and a young son living elsewhere in Kolkata.

"They call me a 'flying' sex worker because I go back home at night and do not stay in Sonagachi. My only fear is that my son will find out about my work. My friend's son found out about her and hanged himself. That is my deepest fear. I have two lives and this is how it must be," the woman said.

The 33-year-old explained that her earnings from the trade have helped her pay for expensive medical treatment for her parents - which she would not otherwise have been able to afford.

"This job has given me money and excitement and even given me a glimpse into high society for a while," explained the woman. "I will continue doing this until clients stop asking for me."

Older sex workers usually see their clientele disappear - like 55-year-old Purnima Chatterjee, who was born into a large and impoverished family and was pushed into the sex trade by her own father.

"I could have been someone's wife, someone's daughter-in-law," said Chatterjee.

"But I don't blame my father for my fate. This was my destiny. God wanted me to bear the burden of raising my five siblings and care for my parents. I have done my duties, by God's grace. But now, I have no one and my earnings have dwindled. What will happen to me in a few years?" Chatterjee wondered.

Fading away

These women are members of a society flourishing on the fringes of mainstream India - a society shunned and condemned in public, but frequented furtively by many.

Although prostitution is illegal in India, the government does not interfere in Sonagachi.

"The government accepts that it is a part of life and society," said Smarajit Jana, the chief adviser of Durbar, a non-governmental organisation.

"No political party in Bengal would want to move them out. Perhaps it is due to the culture of the state, its history of communism and sensitivity towards the marginalised."

In 1992, Durbar took steps to unionise the sex workers of Sonagachi. The rationale was simple - the power was always on the side of the client, who usually preferred not to use condoms.

By forming a collective of sex workers, Durbar empowered them to say no to sex without condoms. The experiment was so successful that in time, 65,000 sex workers across the country would join this collective.

Today, all the sex workers of Sonagachi are members of the union, and they refuse to have sex with their clients without a condom.

Durbar also helps newcomers to Sonagachi, taking them off the streets and housing them in temporary homes.

Two weeks of intensive counselling takes place to ascertain whether these women are minors, and whether they have been trafficked. Minors are handed over to the state government and reunited with families. Women who are open to other forms of employment are trained in various vocations and placed in jobs.

Those who still want to enter the sex trade are taught to protect themselves from sexually transmitted diseases and informed of their rights.

According to Durbar, every year between 800-1,000 young women come to Sonagachi, hoping to make money for a better life.

But Jana said that Sonagachi's brothel model is slowly dying out.

"Real estate development and the advent of technology have already wiped out brothels in other parts of the world, including in Kamathipura in Mumbai," he said.

"In the past two to three years the trend has set in. Land prices have gone up in the vicinity of Sonagachi and realty developers are eyeing the area. The mobile phone has provided anonymity and an alternate means of doing business for sex workers. Sonagachi is fading away, although slowly," said Jana.

Not by choice

As dusk falls, it is time for business to begin. Young women dressed in skimpy clothes and carefully applied makeup line the streets of Kolkata's Chittaranjan Avenue, where customers abound.

The many temples in Sonagachi have shut for the day. Bollywood music floats on the air, accompanied by laughter from houses with names like Night Lovers and Love Nest.

Purnima Chatterjee is wistful.

"Most of us are not here by choice," said Chatterjee.

"We are here to make money and give better lives for our loved ones. We are judged and condemned but we too are doing what everyone else is doing - trying to make our dreams come true and keeping hope alive in the worst conditions," Chatterjee said.

Chatterjee's eyes have a far-off look. Her gaze settles on the pimps lining the filthy streets of Sonagachi - where the holy Ganges River gushes furiously out of open taps and pipes, running its purifying course through the homes of the Sonagachi women.

Follow Sandhya Ravishankar on Twitter: @sandhyaravishan