Fears over new Calais 'jungle' in EU capital
Each night, the youngsters – mostly Sudanese and Eritreans – take over Parc Maximilien, a sliver of green space adjacent to the gritty Gare du Nord station where trains depart for Belgium's North Sea coast.
As in the French port of Calais, the dream of most here is getting to Britain.
The young men, gathered just three kilometres (two miles) from European Union headquarters, have survived a long and dangerous journey through North Africa, across the Mediterranean and the gauntlet of police checks set up to catch them throughout southern Europe.
"This is too hard," said Adam, 25, speaking to AFP, who left his native Sudan and waited for six "very tough" months in Libya. "I want protection from the government (in Belgium). The dream is achievable here," he added.
But for now, only the efforts of activists and charities cushion the indignities of being an illegal migrant.
Belgian authorities want no part in even a temporary solution for people they say are only interested in reaching Britain.
Adam, like many of the 500 to 600 people processed in the park by charities this month, has been caught out by Belgium's clear preference that he quickly move on.
Theo Francken, deputy minister in charge of immigration, has said there is no reason to take on board "illegals ... who do not want asylum in Belgium".
Also hanging over migrants is the EU's so-called Dublin rule, an obligation that asylum seekers lodge their cases in their first point of entry in Europe, which for the majority is Italy.
In theory, migrants could be rounded up and sent back to Italy at any moment, though Belgian authorities have yet to carry out any such operation.
Aid groups such as Medecins du Monde (Doctors of the World) provide medical attention and warn of police harassment.
Stephane Heymans, head of operations for the NGO, said that children make up nearly 20 percent of the migrants and "don't know that they have special rights in Belgium".
Every night, volunteers from NGO Belgium Kitchen make their way across the park, wary of building up a crowd that could alarm residents and create even more problems.
Young men stretch out on the grass, hanging laundry from playground fences, but by dawn the Parc Maximilien will mostly return to normal, as they head into the railway station or continue their journey north.
That journey holds dangers, with high risks of police checkpoints along motorways, at train stations or at the busy port of Zeebrugge.
Police in the coastal province of western Flanders said they have averaged about a hundred arrests per week since the start of the year.
The spectre of Calais, just across Belgium's French border, remains.
French authorities shut down the notorious "jungle" camp there, at its height home to some 10,000 people living in dire conditions, last October.
The town still remains a springboard for people trying to reach Britain by stowing away on lorries heading into the Channel Tunnel.
In Brussels, a Sudanese teenager was killed in July trying to hang onto a bus heading for Britain from a busy terminal near Parc Maximilien.
"A sad first for Belgium," Medecins du Monde said in a statement.