Grown-ups say a lot of silly things to children. By the time I was eight I had been told that the Moon was made of cheese, that Santa Claus lived at the North Pole and that our cat was now in a place called heaven. How unbelievable, I thought, but there were other things that I did think were true.

One of them was the million theory. This was that it was impossible to actually count to a million. The number was too big and so the idea of a million was just that, an idea. Another thing I believed was that Crater Lake was so deep as to be bottomless. Only Wizard Island - the tiny, piney rock that rises out of its deep blue - knew if there was even a bottom at all.

You may have never heard of Crater Lake but then you could not possibly be from Oregon on America’s west coast. We went most years as we crossed the Cascade Mountains, because it was beautiful, educational and a surefire way to avoid stopping off at the nearby cowtown of Medford. Crater Lake has been a national park since 1902 and its lodge is as beautiful as the view.

The lake lies at an altitude of 6,164ft, covers an area of 21 square miles and is ringed by sheer cliffs that rise up to 1,968ft. Wizard Island is tiny but 778ft high. The lake is too blue to be true. The sky cannot compete, even on a good day.

Long long ago - I now know it to be 7,700 years - there was only Mount Mazama here. Legend has it that the mountains had a huge battle and Mazama, which was the Spirit of the Underworld, got the worst of it. The evidence is there for all to see: the mountain imploded, leaving a huge caldera that filled with water. The volcanic peak of Wizard Island formed in more modern times and the lake takes its name from the crater on top of this island.

Kent Taylor is a man whose name matches his job as chief naturalist here. He tells me what I must have known. Crater Lake is 1,932ft deep. This makes it the deepest lake in the United States and the seventh deepest in the world. In the late Eighties a little submarine even went to a few spots on the bottom and it all looked rather normal. Except, Kent notes, they did find something called blue pools: these are depressions some five to six feet across that are filled with a fluid heavier than water. Somehow these are linked to the magma.

It seems right that the erasure of one mystery begets another. I ask Kent if he believes it is a magical place. “I don’t believe in things like that. But I do believe that certain landscapes can inspire people and I think Crater Lake can do that.”