I discovered a wonderful thing the map can do.

If you hold your hand half an inch above it and gently run it over the entire surface it transforms itself into a map of your world. Everyone has a private map of their world stored inside their head, places they've lived, places they've visited; fondly, or not so fondly, remembered.

The map of your personal world is inevitably far smaller than that of the real world. It turns out to be mostly ocean, great blue swathes of it, dotted here and there with small islands that represent the places you have physically been.

If you touch your finger to one of these islands it will instantly expand to show varying sizes of dots depicting the location of familiar towns and cities in that particular region of your world. And if, in turn, you touch your finger to one of these dots up will come a detailed street map.

It will show the streets where you lived or worked or spent your leisure time. Things will adjust their proximity to fit with your recollections. Suburbs will bleed naturally into symbols depicting the hills and valleys where you once took a country stroll. The airport near the resort where you spent a holiday will seem to be mere walking distance from your hotel, which, in turn, will appear only a short hop from the beach.

This is your world. The way you define it in your subconscious. It is a map of recollection, constructed from grids of nostalgia, memory lanes for you to trace with a finger of reminiscence.

And when you do, another wonderful thing will occur.

The map will offer up more. You will find yourself assailed by familiar sounds and scents. The excited voices of childhood friends in the schoolyard, a familiar song, underpinned by the bass on a familiar jukebox, the hazy aroma of hyacinth in a summer garden, the sweetness of satay sizzling on a street vendor's stall.

You'll spend hours obsessively re-exploring your world.

And you will find, as I eventually did, a small and unfamiliar island. A place you never thought you had been. And when you press your finger to this island all that will come up in relief will be symbols depicting forests and mountains.

You will be confused. You will think that the wonderful map has somehow malfunctioned. But something, some raw feeling, will make you hesitate with finger paused on the parchment.

And the sounds and smells will come to you - the verdant fragrance of dense vegetation, the distant caw of a bird, the rustle of leaves, the groan of the branches. The garbled chatter of strange voices.

And you will know exactly where you are.

This is the one place we have all been. The place where the tribe from which we descend came down from the trees, nursing the first kernel of intelligent thought.

This is Eden.

And its remembrance will make you weep.