Here the air is foul: swamping heat and a stench of cigarette smoke, sweat and alcohol. The scene is that of an epic tragedy.
The Muslims are lying in their hundreds across every square foot of floor: old men and women, unshaven youths, crushed girls. Dispossessed, destitute, broken people, the flip side of 'ethnic cleansing', sitting amid a few possessions: a heap of blankets, a frying pan, a broken dish. And thanks to us, they have a packet of soap to last a family a month, one-third of a tin of tuna for each man and no hope of going home.
Is it any wonder some of them are swigging slivovitz? Or weeping under blankets? These are ordinary Europeans, just like us, with faces and eyes like ours, with home addresses and insurance policies and mortgages - although, of course, the policies and mortgages and homes are irrelevant now. Nessima Hotic and her three children came from No 35 Kamicak, Klug, Bosnia - a three-bedroom house with a big kitchen and a television set bought on the never-never. She looks like any English mother, scolding her 13-year-old, tired of entertaining nine-year-old Ismet.
She even talks in a matter-of-fact way. No emotion. No tears. 'My father, Donja Sansa, lived near us. It was my cousin who found out what the Chetniks (Serbs) did. They locked him in a house with old Osman Lovic and four others, and set fire to it. They were burned alive. That was on 25 August. The Chetniks came to Klug on 5 September. They just came into our home and started taking things.
'First they took the table and chairs. Then they took the fridge, then they took the television. In the end, we were left in our empty home. Then they ordered us to leave, lots of us in an open truck. There were six bodies on the road. They were the bodies of Rifet and Meissour and Mousib Disdarovic, Hussein Bajrekarevic, Jafet Bacirovic and Ayoub Potic. All of them had had their fingers cut off. Their noses had been cut off, too, and their ears.'
Mrs Hotic's husband works as a builder in Moscow; she has no idea if he is still there, and he cannot know that his family survives. But, of course, many people are anxious to keep them alive. Down at Split, a young Texan running the UNHCR office in an old Yugoslav plastics factory told me he had a plan to save the life of every refugee in Bosnia, provided the right tents, windows, sheets, blankets, food, milk, floors and lavatories arrived at the right place of misery at the right time. Winter, we have all been told, is the great enemy: we must stop the frost from killing Mrs Hotic and her family.
But this is a lie, a necessary framework to support the most convenient, easiest lie of all: that Bosnia is a humanitarian problem. We must not let the people freeze; the temperature is what we must worry about. As if the catastrophe is some kind of natural phenomenon - such as an earthquake or a flood - rather than a massive war crime.
Upon this poisonous premise, the United Nations has foundered. True, the Cheshire Regiment now drives its white-painted armour through the smoky, cold, steel city of Zenica. But these soldiers are not here to defend it; they are here to protect the 'humanitarian aid' convoys.
And the UN itself is perpetuating this mendacious policy. Its spokesmen now talk of 'warring factions' in Bosnia as if these forces are unrepresentative, equal in immorality.
The UN, you see, must remain 'neutral'. For this, as we journalists have decided in an equally wicked turn of phrase, is an 'ethnic conflict'. Only fools would get involved in such barbarism.
But it is not an ethnic conflict. The hundreds of Muslims in the Zenica gymnasium and the 34,000 refugees in the rest of the city are ethnically no different to the Croats or the Serbs. No one in Bosnia has been 'ethnically cleansed', to use the Third Reich expression that we have so enthusiastically adopted. They have been slaughtered, raped and dispossessed because one community, that of the Muslim Slavs, is weaker than the two other communities, the Serbian and Croatian Slavs.
That is why old Amid Pasic and his wife in the Zenica gymnasium were forced to walk in rags through Bosnia for three months, after being driven from their home in Rogatice, their son cut in half by a rocket-propelled grenade as he tried to defend the village of Oravitce.
That is why the frail, pretty, dark-haired Narka Bonzalek is sitting with her son and unshaven husband on the floor at Zenica. She lived at No 70 Peta Mecave, Banja Luka. She was a nurse in the local hospital; her husband ran a car-wash service.
But on 20 October, all the young men in Banja Luka were told to join the Serbian army. 'Anyone who would not join had to leave their homes,' she said. 'They gave me a paper to sign that I would never return to my home, that all my property would belong to the municpality. They made me pay my telephone bills and my electricity bills before I was allowed to sign the paper. They put us on a bus under UN 'protection'. Then the UN left us, and the men were all beaten. Now everything we ever had is gone. I signed it away, didn't I? Look at us.'
Exactly two months to the day before Narka Bonzalek signed away her home and happiness, the mayor of Banja Luka had told me, at a sumptuous meal opposite his town hall, that no Muslim would ever be forced to leave his municpality. He was lying. He wanted their property. Now he has got it.
We, however, can rest content. We will be helping to keep Mrs Hotic and her children alive this winter. And Amid Pasic and his wife. And Mrs Bonzalek and her husband and child. On television this Christmas, Britons can watch their own soldiers playing King Wenceslas in the snow, carrying winter food and fuel. Thus can we assuage our consciences in the face of evil.