Arriving at the port of Goalundo Ghat, you would never guess that it houses a brothel visited by 3,000 men every day. It is a dusty town filled with long queues of trucks, shops with corrugated iron roofs lining the main street either side of an old railway line, and men, boys and the occasional goat strolling around. Walk just a few paces down a tiny sidestreet, though, and you come to another world entirely: Daulatdia, the biggest brothel in Bangladesh. A settlement big enough to count as a village in its own right, this mass of alleyways is where 1,600 women and girls live and sell sex.
The brothel opened 20 years ago, making it the newest and largest of the 14 recognised brothels in the country. It is set on the meeting point of two vast rivers, the Jamuna and the Ganges (known locally as the Padma), which makes this a very busy place to catch a ferry. Trucks carrying rice, jute, sugar cane and fish from the west and south-west of the country queue here for two or three days at a time to cross the river for the drive to the capital, Dhaka. In Bangladesh on a BBC World Service boat to look at the impact of climate change, I was surprised to find that an unexpected consequence of rising water levels is the growth in demand for prostitution. River erosion has meant the closure of some ferry berths, so men wait even longer to cross the river. And, while they wait, many of them pass the time in the company of Daulatdia's women.
The brothel feels like a vast street market. There are lines of fruit and vegetable stalls, tea stands and even a TV repairer. The only immediately visible difference between this and all the other small towns I've visited in Bangladesh is the presence of so many women in public. These alleyways hold 2,300 single-storey rooms with corrugated iron ceilings and cloth walls. Late morning is the peak time for business, and there is a long taxi rank of cycle rickshaws waiting to take the men back to the quayside when they have finished.
Bangladesh isn't the only country with entire villages devoted to prostitution. In Cambodia there's the notorious Svay Pak, and there are Indonesian villages that house 600 prostituted women at a time. The extraordinary thing about Daulatdia is its size and its unexpectedly open atmosphere. Turning down an alleyway, I am directed past a piece of fabric draped across a doorway and find myself in the middle of someone's room. A post-coital client is enjoying a cigarette, and hurriedly ties a sarong around his waist, scuttles off the bed and away. There's a TV, a DVD player, a fan and a glass cabinet containing clothes. This is one of the better rooms. The woman who rents it can afford to employ a cook - a retired prostitute who is crouching outside in the narrow alleyway, preparing a chilli omelette.
In the next cubicle I meet Parveen, who is happy to show me around. Her double bed is covered with a bright sunflower-patterned throw and she has cut hundreds of tiny holes in the dark red fabric that hangs as a wall behind her bed, giving the impression of fairy lights. She says it's not hard to find clients. "It's OK because I groom myself well. I spend two hours getting ready and then I wait outside. If I want to earn 100 taka [75p] I have to spend at least 40 taka on my face and clothes." One hundred taka buys two big bottles of Coke. Parveen is in her 20s, so her fee is lower than for some; the underage girls can earn as much as 10 times this amount.
As an independent prostitute, Parveen can keep any remaining money once she has paid the high electricity charges, her rent and the cost of childcare in a local village. "I left my two children outside the brothel because I don't want them to grow up in this environment." Yet more than 300 children do live inside the brothel with their mothers, kept under the bed or outside with the cook when a client arrives. The women I meet tell me that whenever they're pregnant, they hope for daughters who can join them working in the brothel as soon as they are old enough.
The bonded prostitutes, known as chukri, have the least freedom. Their average age on entering the brothel is 14; they have usually been kidnapped by gangs, sold by stepmothers, or lured here by boyfriends with promises of good jobs. I meet a bonded woman who is dressed in a pretty red sari. She tells me that she must see three or four clients each day and then another during the night. "I've been here 10 years after I was trafficked and someone sold me. I'm from Chittagong, a port far away from here." She pauses and then says: "I'm really not happy." After a fixed period of time, bonded women can buy their freedom. She hopes to do so within the next year or two. No longer a slave, she would in theory be free to leave. But despite the fact that she was kidnapped, her family won't have her back because of the shame associated with her job, so the most likely outcome is that she will stay here and become an independent prostitute.
In the brothel hierarchy, those who are bonded have the least freedom, but even those who chose to come here tell me that they felt they had no alternative. In research at this brothel in 2005, the humanitarian organisation Terre des Hommes found the main reasons for entering the brothel to be poverty, deception, abuse and coercion. Parveen arrived 10 years ago to escape from a husband so abusive that it was worth the risk of meeting violent clients here, she says. "I was married, but my husband violated me so often that in the end I couldn't bear it any more, so I came here."
Despite Muslim strictures on sex outside marriage, there are 100,000 women selling sex in Bangladesh. And clients are surprisingly open about the fact that they visit them: my BBC baseball hat and large microphone didn't deter them from speaking to me. "I'm a businessman," says one, "so I stay in the port overnight and then leave next day. I always visit the same sex worker." Is he married? He nods. And does his wife know he comes here? He laughs, "Oh, no, she doesn't know."
Landlords and madams profit from the women selling sex, but so do others. The grocery shops, tailors and fruit stalls all overcharge for goods sold inside the brothel. Affording the basics is so difficult that hope of winning the star prize of a plastic cup or a bar of soap attracts plenty of women to the safe sex workshops held in the afternoon. They sit on mats in a leafy courtyard, immaculately dressed in red, orange and yellow saris, while a plastic phallus is passed around for condom-unrolling practice. The safe sex workshops are run by the Bangladesh Women's Health Coalition (BHWC), with funding from the World Bank and the Department for International Development. The women sleep with an average of 19 clients a week, and 60% say their last client didn't use a condom. Despite this, the official HIV rate among sex workers is low - just 1%.
A group of prostituted women have been specially trained to teach the others about safe sex. Mrs Pankee, who is running today's class, holds up an unforgettable, laminated photograph of ulcerated penises covered in suppurating sores, warning the women to avoid touching them. The women are assertive and seem to know plenty about safe sex, telling me they throw men out if they refuse to use a condom. The bonded prostitutes are most at risk because their madams often agree to let men pay more for not using a condom. Ever determined to find a way to get the message across, the BHWC has introduced the Best Madam award for the madam who knows the most about safe sex.
But there is one group of clients that doesn't traditionally use condoms. These are the women's long-term lovers - known as babus - who often run shops within the brothel. The women tell me, "We've known the lovers a long time, so we don't mind not using condoms with them. We love them, so we trust them." But with many of the babus having wives back at home, the fear is that they might act as a bridge population spreading disease into or out of the brothel. A group of babus cheerfully tell me that they enjoy the men's safe-sex classes so much that they come every afternoon. Each of the eight men insists that they always use a condom. As we turn to leave the courtyard, though, BWHC's deputy executive director, Julia Ahmed, says: "They are lying to you. I really don't think it is the whole truth."
The far end of the main alleyway gives way to a green field where a few goats are grazing. For the first time I can see the sky and hear the birds singing. This is where some of the women will end up. In 2000, the high court in Bangladesh declared that prostitution is not illegal, but there's no doubt that it remains taboo: women in prostitution here have no rights to burial in consecrated ground, so this peaceful field behind the brothel is their graveyard.
Not that anyone I meet intends to spend their whole life here. Each has a plan to leave, just not quite yet. "I know I have to go out at some time," says Parveen. "I'll stay here maybe one or two more years. I would prefer to leave the country, but I don't know what sort of job I could do." The women know that they will find it hard to start anew due to the way they are viewed by the rest of society; the same society from which 3,000 men come to visit them every day. To rid themselves of the shame they feel, the women often give some of their hard-earned cash to the beggars hanging around hopefully in the brothel's alleyways. One woman tells me she has been thinking about leaving for 10 years in order to build a small house for her and her two children. But Ahmed isn't optimistic about their life chances outside Daulatdia. "Sometimes they leave, but they always come back. They can't get work outside. They get habituated to this profession and this environment, and they find it cosier here."
Intrigued, I ask one woman whether there is anything good about living here. I'm hoping it's not all as bleak as is seems, that perhaps she will tell me there's a sense of camaraderie among the women and girls. Instead she looks at me with dull eyes and says: "What could be good about living here? I'm just here for survival. If I were outside, I'd have my husband and my family, but in here I have to receive different clients all the time. You want to know what life's like here? We don't have a life".