Latin America's secret slave trade
Everything from fake branded clothing to Class A drugs are ferried back and forth along these clandestine routes. The list of contraband goods now also extends to human beings.
The human-trafficking business is estimated to be worth over £10bn a year, making it the world's third most profitable criminal activity after drug-smuggling and gun-running.
Many of those trafficked through the triple frontier are destined for the illegal labour market in Brazil or Argentina. The trade in babies for adoption is also widely reported. But a large proportion end up as sex workers. Many end up in brothels across the region, although a high number are destined for the triple frontier's own thriving sex industry.
Children are particularly vulnerable to human traffickers. Charities working with at-risk children in the border region estimate that as many as 3,500 young people could be involved.
"Many girls are trafficked via the pique. It's all highly organised", explains Marcelina Antunez, director of Luz de Infancia, a children's care centre in the Argentine town of Puerto Iguazú.
Driving the trade is the flood of foreign tourists who come to visit the world famous Iguazú waterfalls. Much of the demand for prostitution is casual. Yet the region also attracts a hardened group of sex tourists.
The region's reputation for prostitution is not new. In the late 1970s, around 40,000 workers flooded into the triple frontier to help build the colossal Itaipú hydroelectric dam. Around 97% of the new workforce were men. As the dam went up, so too did the demand for paid-for sex.
"The triple frontera is the Bangkok of Latin America...after the tsunami, many sex tourists started coming here instead of Asia," notes Cynthia Bendlin, director of the International Organisation for Migration (IOM) for the triple frontier area.
IOM runs a number of awareness programmes to highlight the dangers of the trafficking trade. But it is an uphill struggle. Many of the children most at risk either live on the street or come from very impoverished families, Ms Bendlin explains.
In some cases of extreme destitution, children are even contracted out by their parents. There is a blind beggar in Puerto Igazú, for example, who walks the streets hand-in-hand with a seven year-old girl. He makes his living by renting her out for sex. She is his neighbour's daughter.
The situation is complicated further by the "recruiters". Often known to the victims, they promise the opportunity of work across the border. When the fictitious jobs never materialise, the victims finds themselves trapped and unable to return home.
IOM also works with local government agencies and the police in an attempt to develop coordinated strategies to stop the traffickers. Again, prgress is slow. In Argentina alone, there are at least five separate security agencies operating in the border zone. Between the three countries, the problem of coordination becomes triply complicated, Ms Bendlin admits.
At a national level, there are some signs of encouragement. This week, Argentina's lower house is scheduled to discuss a bill that would officially recognise underage human trafficking in the criminal code.
Victim organisations welcome such measures, but remain sceptical about how much difference they will make on the ground. Argentina, Brazil and Paraguay all have separate laws and legal processes. Add to that the variety of municipal, provincial and national legislation and you have a complex legal web to navigate.
It is a journey that many victims would rather not undertake. In addition to the psychological and financial implications of pursuing a court case, many fear the threat of reprisals.
"Although we know about more than 700 cases of child trafficking, we have only reported 40 in the last three years", confesses Benigno Cáceres, a lawyer with CEAPRA, a children's charity in the Paraguayan border town of Ciudad del Este.
Only one of these complaints resulted in a guilty verdict.
The relative impunity for sex-related crimes is in keeping with cultural attitudes in the triple frontier. The region's strong culture of machismo holds that sex with underage girls is safer and a sign of male virility, says Norma Pereira, a child psychologist in Ciudad del Este.
In addition, the mothers of trafficked children are frequently themselves the victims of abuse or involved in prostitution, she explains: "Families often refuse to recognise the problem. It's as if this new form of slavery has become natural."
· Oliver Balch is a freelance journalist based in Argentina.