In Rio de Janeiro

Nothing stays in sport. Especially not Usain Bolt in one place. He has the baton in the 4x100m relay and he is gone. "There's no one on the anchor leg that can outrun me," he says. Such truth cannot be bragging.

Bolt works in seconds and we can honestly say we have watched almost every one of his at the Olympics. Through 23 races in three Games he has been on the track for a total of 410.25 seconds. In less than seven minutes in eight years he's won nine gold medals. And turned cynics into fans. At the mixed zone, reporters hand him posters to autograph and shoes to sign and squeeze themselves into wefies. Journalistic impartiality just got run over.

It's 12.35am and not yet the end of a day which began at 12 noon in a tennis stadium without a court. Somehow I sneak into the main stadium at the tennis and find there are no lines any more, no posts, no net. Just a patch of paint where the court was. I stand on the Olympic rings behind the baseline on a blue-sky day and not far from me is where Novak Djokovic cried days ago. But there is nothing here now, only ghosts and silence. The Olympics are ending.

Broken sporting dreams never leave any debris. Everything gets swept up and pain gets taken home. Nothing stays except shards of memories. Some days ago, a high jumper of unknown origin walks through the mixed zone, his face a twisted mask of grief. At one point he stops, crouches, as if emotion has stilled him, then he rises and walks. "Do your best," everyone says in sport. Sometimes you just can't.

I will tell people I went to Rio but I never saw the city except from the window of a bus. My world is primarily Olympic Park - a small town with a laundry, a bank and a post office - where I have spent 20 days. And so on Friday, I take a slow two-hour walk through its premises because I can never come back here again. In a few days it will not exist.

I take a look at Joseph Schooling's pool - for us, that is what it is - and already it's changed. The lane markers have gone and a net is inside the pool. Women are playing water polo. I peek into the interview room and empty chairs sit in a quiet line. Just days ago Schooling was sitting here in the midst of Michael Phelps, Chad le Clos and Laszlo Cseh and saying graciously: "I have the least medals out of these guys."

Nothing stays the same because the Olympics changes people. Two women runners trip over each other and then stop mid-race and help each other up. Their training is in running and winning and they have not practised this decency. It just comes, instinctively, which is what makes it compelling. They have found their best.

It's a sunny day and I haven't seen a mosquito for weeks. The soldiers must scare them. The crowds at the gymnastics and beach volleyball have been my favourites because never have I felt more like dancing than when in their midst. To keep my reputation intact I kept sitting.

I stroll into the Maria Lenk Aquatics Centre, where the diving pool is silent. Only the ghost of Ilya Zakharov lingers, the 3m springboard champion of 2012 who earned a zero here. He is a lovely diver but jokes abound about his belly-flop. How does one man's misery become our pleasure?

Only once in 20 days have I looked at the medal table because it doesn't interest me. Numbers rarely do, stories always will. Like Ryan Crouser's. The shot-putter says he studied the Olympic record-breaking throw of Ulf Timmermann from 1988 roughly 10,000 times. Have you ever watched anything 10,000 times? Do you understand obsession now? In Rio, Crouser honoured Timmermann's throw by breaking Timmermann's record.

Or take Madeline Hills of Australia, a full-time pharmacist who runs in the dark before work and sometimes after and now in Rio she comes 10th in the 5,000m. It is a personal best. We venerate stars but it is from these small tales, this commitment to a cause, this defiance of obstacles, that the Olympics still find meaning. Hill's reward is not a medal but satisfaction, no running for two weeks and a "little more wine and cheese".

Friday in Rio is ending but the audience can't leave the athletics. It's a full house, it is Bolt's house. People through history have lost at these Games: Paavo Nurmi did, Carl Lewis did, yet Bolt never has. People win sprints by fractions, Bolt wins by metres. Damn, he has spoilt us.

He appears, a roar. He waves, a roar. He runs 20m to limber up, a roar. He gets the baton in his left hand, a roar. He takes off, a roar. He reaches the line first, a roar. This is the sound of speed.

Then he is gone and the only thing I think is this: Nothing stays. There will be someone better than him because history tells us there always is. A kid chasing sheep somewhere. A kid not yet born. A kid like him who loved sport. Just coming from nowhere to surprise us. Another bolt from the brilliant blue.