The first time I saw it, I thought of a mirage.
A sudden, glittering, shimmer of lights and colour down a gloomy side street a few blocks from our house.
The next time, a week later, I turned the car round to get a closer look.
The northern suburbs of Johannesburg are a pleasant sprawl of tree-lined avenues, and comfortable houses hidden behind high security walls and electric fences.
The mirage turned out to be a trolley - a supermarket trolley, enclosed within a wire cage, and carefully, extravagantly decorated with hundreds of shiny compact disks and ribbons.
A tall, lean man in a shabby black raincoat was pushing the whole, precarious, structure along the road.
It seemed such an absurd, beautiful sight that I realised I was grinning broadly.
And for almost two years now, it's had the same effect on me, every time I catch a glimpse of the trolley - it's like a snatch of song, or a warm memory.
It's actually seven years since Solly Radili first started work on his walking mirage.
"She is art, he told me the other day, as we sat in a patch of shade. I am her spokesman," he says.
Solly is not sure how old he is, but he was born in a rural settlement not far from the border of what is now Zimbabwe. He never went to school; had an arranged marriage at the age of 17, to a girl called Maria; and soon afterwards, in about 1955, came to racially segregated Johannesburg alone looking for work.
He got a job cleaning and gardening for a white family. "I was a houseboy", he says - an apartheid label that still lingers in these suburbs even today.
For a short while, Solly left the city to work on a building site near the coast. But he drifted back to Johannesburg, and ended up walking the streets looking for scrap metal to sell, and sleeping rough in Joubert Park near the city centre.
The decades slipped by. He sent a little money home and visited Maria from time to time. They had four children, but Maria became an alcoholic, he says.
"Not me - I never drank once."
In 2003, Solly was pushing a trolley through a smart neighbourhood, looking for more scrap metal, when a white woman came out of her house and gave him three old CDs.
"I put them on the front," he says. "I like the way it looked. That is how I started".
As we're talking, he takes a pair of scissors out of his pocket and carefully cuts a strip of cloth. His long nails are caked with dirt, his brown trousers and woollen hat, threadbare. But somehow he manages to look almost dapper - like a tailor - as he neatly threads the cloth to the back of the trolley, just below a South African flag, a CD and a Winnie-the-Pooh teddy.
Solly is on his fourth trolley now. Two were stolen by scrap-metal hunters. One was confiscated by the police when he was visiting his family. "Now my youngest son is a drunk and a layabout," he says.
"I went home for a traditional ceremony, to try to cure him. It didn't work. This trolley, number four, is my best yet."
He parks it every day on the pavement near a small shopping centre. People stop and give him money. "Some want to take my photo," he says. In a day he can earn 70 rand ($10; £6).
It's noon, and a white woman walks up the street and hands him a sandwich. "I try to give him one every day," she says. "He is a wonderful man. We love to see his art."
Solly sometimes features in the local newspaper. He's portrayed, perhaps a little patronisingly, as a rather mystical figure - a man with no past, driven by some instinctive force to create art.
Solly shrugs. "They say this is art, and it makes them happy, and because of that, I don't starve. But I'm not trying to make a statement. White people like it. And I love them for helping me."
But Solly is more than a busker.
A local art gallery offered to buy his trolley, but he refused. Not just because it's his livelihood, but because he felt the gallery would somehow be cheating - taking a short cut. "It takes time to make this," he says proudly. He seems to be growing into the role of an artist. "Someday I will make something else. Something very different."
These days he is no longer sleeping rough. One of his admirers lets him roll out a mattress in his storeroom every evening.
"It's not safe on the streets at night," Solly says. "There are criminals everywhere today, and no truth in politics. It was better before."
On cold mornings he sometimes considers retirement. "I'm broken," he says. He must be at least 70.
But then he takes another bite of his sandwich, puts his scissors away, and stands up to admire his trolley, glittering in the afternoon sun. "I'm fit. I'm healthy. I can go on for years."
This was written for From Our Own Correspondent.