This is a sticky one. The cleanest country in the world is generally agreed to be Switzerland. Its streets are so clean you could eat off them. With the Swiss forever pruning their trees, polishing their mountain tops and scrubbing their house-fronts, how can the Germans compete? Well, let me put it this way: Basically, the Swiss are just an extreme form of Germans. We shouldn't allow our own achievements in the field of cleanliness to be overshadowed by theirs.

I call Johann Wolfgang Goethe as my first witness. "Let everyone sweep in front of his own door, and the whole world will be clean," he said once, not only coining a phrase but also expressing a core truth about the German identity.

On the one hand, he means you should clean up your own mess and keep your nose out of other people's business. But on the other he might have meant it literally, too. Germans do love to sweep. As the 20th century German philosopher Otto Friedrich Bollnow once said: "When the tradesman has straightened his shop, when the housewife has put the whole house into clean and shining condition, and has even swept the street in front of the house ... then a deep warm feeling of resting settles down over the people."

This feeling is so deeply entrenched in the German psyche that in some parts of Germany, such as Swabia, it has been institutionalized as the "Kehrwoche," (sweeping week). This is basically a rotating system whereby residents in an apartment building are each assigned a particular week during which they are responsible for cleaning the building's steps, cellars and sidewalks. Everyone knows whose turn is when and everyone is keen to make sure the duty roster is adhered to. It's all perfectly friendly, of course. Ahem......

It's not only the streets that need to sparkle. Clean laundry is the ace up Germany's sleeve. When I was growing up, it didn't matter if my socks were darned, so long as everything was freshly laundered. My mother wanted to be sure that if I ever had an accident, I wouldn't end up on an operating table in dirty underwear. How mortifying would that be?

Germany: all kinds of clean

Beer, for example, has to meet the standards of the German Purity Law. We also like cleanliness in the figurative sense. Freidank, a 13th century Middle High German lyric poet, and coincidentally from Swabia, wrote, "Whatever the sun touches, the sunlight keeps pure. However the priest may be, the Mass is still pure. The Mass and the sunshine will always be pure. "

We Germans firmly believe that when it comes to matters of purity and hygiene, you can't start too young: the German word for toilet training is Reinlichkeitserziehung, that's cleanliness training to you and me.

Now please wash your hands.