Three Coins in a Fountain - made famous by Frank Sinatra and sung for the 1954 film of the same name - has raised a lot of money for charity over the years.
The morning we visited the beautiful Trevi Fountain in Rome there weren't just three coins but thousands of them being sucked up by a high-powered pool cleaner, poured into big canvas bags, padlocked and then stowed away in a solid-looking van.
The water wasn't running while this was going on but we were happy to wait and watch the fun.
Half-a-dozen armed police were there to ensure no one tried to hijack the load and in their idle moments they hassled a few scruffy vagrants who were hanging around the square.
One, who could speak a bit of English, saw me taking photos of the heap of coins and commented a bit contemptuously, "that American film has got a lot to answer for. Now every tourist who comes to Rome has to come here and throw a coin in the water".
There is said to be a local legend that if a tourist throws a coin in the fountain it means they will come back to Rome one day. But my policeman friend sneered, "no one had ever heard of that legend before the Americans told us about it".
My wife had brought a coin with her to toss in the fountain but I didn't tell him we, too, had been seduced by the story.
Anyway, I've read they take €3 000 a day from the fountain and use it to help feed Rome's poor, so it's a custom that's done a lot of good.
There was more fun on offer when the coin cleaning was over because there seemed to be a problem getting the fountain to go again. Eventually a workman in overalls and gumboots had to climb on to the fountain with a hose and stick it into various orifices to get the water moving.
With the water flowing over the marble sculptures of ocean gods and sea horses - the theme of the fountain is "Taming the waters" - and the early morning sun reflecting off its waterfalls, it was certainly a magnificent sight.
It's hardly surprising that in the three centuries it has stood there various legends have sprung up about it. The latest, according to an American woman who was waiting with us for the water to start flowing, is that if you throw in two coins you'll have a new romance and three coins will mean you're heading for marriage or divorce.
Since this was a 40th wedding anniversary trip it was probably a good thing we only had the one coin to throw. - New Zealand Herald