Across the river, the multi-billion euro Belgrade Waterfront project, a development of luxury apartments and retail outlets, is under construction: cranes looming above half-built penthouse flats, shopping malls and high-end hotels.
But just a few hundred metres away, tucked behind the station, an abandoned building holds a tragic secret.
Once used to repair broken down railway stock, the warehouse has not been used in decades. Its doors and windows are broken, the icy Serbian winter wind whistling through the gaps across the rough, concrete floor.
On a patch of scrubland outside the warehouse, among piles of rubbish and burned-out fires, eight-year-old Aziz is playing football. He is the youngest of a group of more than 1,000 male refugees living here, most of them from Afghanistan and Pakistan.
The men, queuing for their daily meal provided by a grassroots charity founded by a former home economics teacher from Wales, have no access to running water or basic sanitation. The toilet is a pile of rubbish behind the warehouse, where rats run among the stinking garbage, while the only water supply comes from a broken pipe.
Although counted in the 7,400 refugees reported by the United Nations’ refugee arm, UNHCR, to be in Serbia, those in the warehouse – known locally as the “Barracks” – are not registered in official camps. Instead, they are living without access to proper aid or support.
Aziz, from Afghanistan, is said to have travelled the 2,500 miles to Serbia with his father, using people smugglers to help get across borders and into Europe, where they hope for a better life.
His father is nowhere to be seen, but he is looked after by a group of older boys and young men, most of whom have been at the camp for a few months.
“I am from America,” he says, a huge smile lighting up his face. His friends laugh. If he was, they tell him, he would not be sleeping here, on the floor of this deserted and freezing warehouse.
Ali, 20, has had slightly more luck. A fluent English speaker – one of many languages in which he can converse – he has made friends with a Serbian man who owns a disused café building on the edge of the camp.
“We were talking and he said he could see we are decent people, so my friends and I are allowed to sleep in the café,” he says.
Unlike the others, who lie among piles of rubbish on a rough and dirty concrete floor, Ali and his friends have a stove with pipes running through the building.
“It is warmer and more comfortable,” explains Ali, a former English teacher whose language skills earned him a job translating for American soldiers in Afghanistan – which in turn, made him unpopular with the Taleban.
“It is enough to say it wasn’t safe for me,” he says. “They came to my house for me twice, but I hid. Then I left.”
He is huddled around a fire inside the main building with a group of friends. The air is thick with smoke. Some refugees have created makeshift heaters, with vents sticking out of the broken windows. “It makes it hard to breathe,” says Ali. “It is full of garbage, which people are burning to keep warm. People have many different diseases, in their chests, their lungs.”
He calls over his friend, Wais, and instructs him to pull up his t-shirt to reveal a long scar down the centre of his stomach.
“The Taleban did this to him,” he explains. “With a knife.”
Ali hopes that one day he might be able to return to Afghanistan to collect his parents. His father, also a shopkeeper, had lofty ambitions for his bright son.
“My father used to tell me: ‘Study, study, study’,” he beams. “And I will do it again.”
Unlike some of the others, most of whom hope ultimately to reach Germany, Ali does not have a particular destination in mind. “I will not say ‘I want to go there or there,’” he says. “It is not about beauty. It is about safety.”
He smiles. “I don’t know what the future is going to be. I can’t predict it, but I can hope. If I lose my hope, I won’t have anything.”
Keen to move as many people as possible into the “official” Obrenoviac camp 20 miles outside Belgrade, the Serbian authorities ordered aid agencies to withdraw support from the site in October in the hope that, by making the camp as unattractive as possible, it might encourage more to move to government-run camps, where the conditions are vastly better.
But the men here – mostly aged between 16 and 35 – do not want to go. Moving to an official camp means they need to be registered and become part of the refugee system – something they are terrified to do.
“If I went there, I would get stuck or be sent home,” says one young man, also named Aziz. “I cannot risk that.”
Only one aid agency has stayed to help the refugees.
UK charity Hot Food Idomeni, which was launched by Cardiff-based home economics teacher Barry Fallon to provide food in the Idomeni camp in Greece, was alerted to the situation in Belgrade and moved in after the closure of the Greek camp in May. It is supplemented with a similar service provided by a Spanish group, which helps out with evening meals.
“We provide them with a meal that is roughly 800 calories every day,” explains Fallon.
“We told the authorities that we were not going to leave when they said we should. Everyone needs to eat. So far, we have not had any problems.”
The camp is also assisted by a handful of independent volunteers, including Nina, from Glasgow, who is helping to chop wood with the refugees.
“I just do whatever needs doing,” she says simply.
Since borders with neighbouring countries were closed a year ago, refugees in Serbia have nowhere official to go in western Europe, creating a bottleneck. Previously, the West Balkan route allowed them to move freely through the region, out through Croatia and eventually into Germany, where Angela Merkel’s government has said it is ready to welcome them. Now they are trapped.
Those living in the former Yugoslavian nation now find it very difficult to leave under the official system. The border with Hungary was closed a year ago and now allows only a handful of refugees to pass every day, all of them on a list from official camps.
Refugees have the right to request asylum in Serbia, but many are keen to move on to somewhere that is less economically deprived, or to another destination where family members have already settled.
“People don’t want to stay here, they want to go further on into Europe where they have friends and family,” Fallon explains as he hands meals to an orderly queue of hungry men. “If you know one person in one place, that is the person you will reach out to when you have nothing.”
Under the “Joint Way Forward” agreement made in October between the European Union and Afghanistan, “irregular” refugees from the country could be deported, although the EU will examine every case on an individual basis. Those deemed to have entered the EU “irregularly”, could be forcibly returned.
The fear has left refugees reluctant to leave the unofficial camp, preferring to endure the appalling living conditions rather than risk being sent back to their home countries. Almost all of the men wear black: dark clothes carefully selected from any donated to them to ensure they would be less visible if they suddenly decided to make a dash for the border when summoned by a smuggler.
However, when temperatures plummeted over the winter, it was too much for some. Aid workers say three groups of around 170 men gave up their hopes of freedom via an illegal route and put themselves forward to be transferred to one of the official camps.
Milena Radakovic, project coordinator at Philanthropy, a Serbian aid organisation which is a partner of UK charity Christian Aid, says that inhabitants of the Barracks are reluctant to move.
“People stay there because they want to be below the radar,” she says. “They don’t want to be visible.”
The Serbian authorities agree.
“Some of the migrants do not want to go to the centres because they are waiting for smugglers, explains Svetlana Palic, spokeswoman for the Serbian Commissariat for Refugees and Migration.
“Others are afraid of deportations or don’t want to leave Belgrade, which is not far away from EU borders, their final destination.”
Aziz, 20, admits he paid people smugglers thousands of euros to get him to Europe, where he hopes to meet up with family members who travelled ahead of him.
“If I had known this was how it would be, I would not have come,” he says. “They told me they would bring me by car, by train. But we walked across the mountains for hours and hours. It was awful.”
Refugees and aid agencies report stories of groups of locals “hunting” migrants on the Bulgarian border, while Hungarian authorities have been condemned for their use of dogs to turn would-be asylum seekers away.
“They took everything, everything in Bulgaria,” says Aziz. “Money, mobile phone. I was left with nothing.”
He pauses. “My life in Afghanistan was very good. There were just two problems: the Taleban and Daesh [so-called Islamic State].”
“You could not go to school, you could not study. Everywhere there was fighting. Every time I went to school, I was fighting for my life.”
He points to the crumbling walls of the warehouse, where some men are still sleeping and indicates young Aziz, who is now crouched on the floor with a ten-year-old companion, Jawed, picking at the meal he has been given.
It is estimated that up to 60 per cent of the people here are unaccompanied minors – young men under 18 travelling alone.
“This, living here, it is a big problem for everyone, big or small,” he says. “But for some of the smaller ones, it is worse.”
By leaving Afghanistan, 17-year-old Ahmed, who is fluent in five languages, has left behind his family – his father, a shopkeeper and his mother. The family has saved to be able to pay for their son to make the journey in the hope he will have a better life. But he does not know when, or even whether, he will see them again.
He is awaiting the arrival of his cousin. When he comes, the pair will contact people smugglers and continue their journey into western Europe. They have already paid thousands of euros to smugglers who have got them this far on their journey.
Once they have been given the go-ahead by the smugglers, they will ask their families to transfer more money through an international cash transfer system and pay it to the smugglers who will, they hope, get them over the Hungarian border and into western Europe.
“My father and mother cannot afford to come,” he says. “They gave everything they had for me to be here.”
He looks around him, where his fellow refugees are squatting on the floor eating their lunch out of cartons.
“They wanted something better for me. They are not thinking about themselves. When you have children you stop thinking about yourself.”
He adds: “We are always thinking about life: we are human, although it may not look like it at the moment. I want to do something in my country, I want to make it good, but at the moment, I cannot.”
In one of the official camps, in Presevo, in southern Serbia, Adnan, 17, from Pakistan, shares a specially constructed tent with dozens of other men. They were all brought here from the Barracks, and another unofficial camp known as the Brick Factory, in the north of Serbia, around a month ago.
Adnan insists the police raided the camp and bundled as many refugees as they could into a bus – a claim the Serbian authorities reject, saying they do “not use force” and instead work with refugees to convince them to move voluntarily.
“I do not like it here,” says Adnan, indicating the rows of neatly made bunk beds behind him. Close by, children are in a classroom, learning the basics of English and German, taught by aid workers, while other men play volleyball on a specially marked pitch a few metres away.
In a separate building, aid workers are preparing one of three meals a day on offer to the refugees in a smart dining hall.
Adnan shakes his head. “The conditions are better, yes, but it is a closed camp, we have no freedom. And freedom, for us, is the most important thing.”