Memo to the International Olympic Committee (IOC): if the sewers in a city are so fragile that you are frequently asked not to put toilet paper down the toilet, said city is probably not quite ready to host an Olympic Games.
I feel so sorry for the Cariocas, the inhabitants of this mesmerising, wonderful metropolis.
Most of them so desperately want everything to be right and for us visitors to have a good time - even those who do not much care for sport.
Most people are so kind: on my first morning in the city, someone I met on the fifth floor of the elevator offered to give me a lift from my apartment block in Botafogo to Barra da Tijuca – the small matter of 40 kilometres – by the time we had reached the ground floor: I left my mobile phone in a taxi the other night and it was returned to me within 40 minutes.
There have been many touchingly wonderful moments, as there always are at these events where the world meets.
I just witnessed one on the train on the way here: a posse of Senegalese fans burst into the carriage all energy and life and within five seconds were swapping selfies with a group of purple-jacketed cleaning staff. Cue instant connections and much joy.
But after two weeks in Rio, it is impossible not to conclude that the biggest circus in sport came here too soon.
There have just been too many untoward incidents, involving bullets, thefts, rocks and now a car accident, too much disorganisation, too many skeleton services.
Even if journalists were soon bickering over who was standing closest to the bullet that pierced the media tent at the equestrian venue, it is frankly mind-boggling that such a thing should have happened.
If the IOC truly thinks the Games will transform Rio, they are deluded.
What they will do, courtesy of the new metro line opened in the nick of time, is accelerate the shift to the west that has already happened.
Barra da Tijuca, where Rio 2016’s centre of gravity lies, is nothing like old Rio.
It is essentially a 20-kilometre-long shopping mall cum condominium park with a superior beach front.
The sheer scale of it is already stunning.
Part of the attraction of Barra, I think, is that it enables local inhabitants, those lucky enough to enjoy a certain amount of disposable income, to design their own lives without the restrictions unavoidably imposed by the extraordinary topography that makes old Rio so scenic and so cramped.
To be fair, when Rio was chosen in 2009 as the first South American host of an Olympic and Paralympic Games, it was possible to imagine that it might just about cope.
Business was booming, with the promise of an oil bonanza to come.
The country had a President - Luiz Inácio Lula da Silva - who seemed up to the job.
The subsequent collapse of oil prices, and the economic and political crises, have highlighted just how big a gamble the IOC was taking.
I would think it will be a good while before they are so adventurous again.
Rio, meanwhile, would have been better off reining in its ambition and adopting the route followed by Buenos Aires by bidding for and winning a more manageable event - the 2018 Summer Youth Olympics.
Rio has also been unlucky in more than the way the economic cycle has fallen.
Normally by now the compelling spectacle of Olympic sport would have diverted attention from many, though perhaps not all, of the sundry noises off.
But the shadow of doping that has hovered over sport for a generation or more has become so dark as to blot out its capacity to inspire.
Sport, for now has lost its magic and hence its ability to take our attention, never mind our breath, away.
This was evident in reactions to today’s searing women’s 10,000 metres final, at the Olympic Stadium where I am writing this, in which Ethiopia’s Almaz Ayana broke the world record by more than 14 seconds and 18 personal bests were set.
Instead of wonder, there was doubt; instead of certainty, questions; instead of inspiration, scepticism.
There have been great stories during this first week of the Games – Michael Phelps (yet again), Katinka Hosszu, Katie Ledecky, Kath Grainger.
But only gymnast Simone Biles has definitively stolen the show from all the other issues.
My Olympics is nearly over now; I will be leaving on Monday.
I will depart, as usual, with new friends, great memories, a sense of gratitude to all those who helped me along the way.
But also with misgivings about how their own politicians and the international sports machine contrived somehow to put our charming, endlessly helpful hosts in an almost impossible position.
The Olympic Games is a unique, unforgiving stress test that searches out any weaknesses in a host-city’s governance structures.
The flaws in Rio’s governance model - and its sewers - have now been exposed for the world to see.