"So, what was your favourite thing here in the USA?" my Californian friends inquired expectantly. "The redwood giants, right?"

"Way to put someone on the spot!" I thought as I squirmed uncomfortably in my chair. I had been about to reply: "The Grand Canyon", but thought the better of it when I saw their eager faces. I mumbled something about it all being really great and how those redwoods really were the tallest trees I'd ever seen.

People, don't ask visitors to name their favourite part of a country if that country is almost the size of a continent. There is never going to be a right answer and somebody is bound to get hurt; as in the classic adulterer's answer when asked, "What does she have that I don't?": "Er … you're both different?"

But it did get me thinking about choosing my finest moment - in China, that is. In almost 25 years of travelling in the country, I have concluded that the best of the bunch would have to be the time I stood with one foot in China and the other in North Korea, taking my weight off the China foot for a few seconds and knowing that North Korean border guards would be hiding in the bushes, pointing machine guns at me.

Yes, in Dandong, Liaoning province, there's a bridge that runs across the Yalu river into North Korea. The river is so narrow that you can see clearly the grey and sunken houses on the other side - a kind of reverse Potemkin village; uninhabited and seemingly made to look as if the country is so poor it can't even afford glass for its hungrily gaping window frames.

A ferris wheel stands motionless, looking as though it has never moved in its life. Seen from frantic and prosperous Dandong, you get the impression that there is nothing and no one in North Korea at all.

But venture farther along the border, into the countryside - where they have, of all things, a little Great Wall - and you'll find possibly the least polluted place in China, the pastoral tranquillity of which is broken only by speakers blasting out North Korean propaganda (or so I presumed it to be) from the other side.

It is here, where the Yalu runs only a few centimetres wide and only a thicket hides North Korea from sight - that some thoughtful person has made, in the metal fence separating the two countries, a hole big enough for an adult to squeeze through.

And there is a sign in Chinese warning sternly against taking photos, laughing at or making fun of people (the guards) on the other side, or throwing things.

Who would actually stand with one foot inside North Korea, with machine guns trained on them, and start chucking things at border guards?

That was probably one of the few occasions in my life when I have completely obeyed a sign. My finest moment.