ONE OF the problems of living as we do in a steep-sided valley - maybe you've never had this experience? - is that the longer you live there the more reluctant you are to leave it. You wallow more and more in splendid isolation. It becomes harder

ONE OF the problems of living as we do in a steep-sided valley - maybe you've never had this experience? - is that the longer you live there the more reluctant you are to leave it. You wallow more and more in splendid isolation. It becomes harder and harder to believe that life, especially intelligent life, exists beyond the hills. Eventually, I suppose, you come to imagine, like some remote Eskimos apparently did before being discovered by Polar explorers, that you're the only people on the planet.

So it needed a real scruff-of-the-neck effort to get ourselves out of our comfortable rut the other day to do a little exploring. It says something for our creeping valley mentality that we went off exploring somewhere we'd explored already, but several years ago. All the same, we made a fascinating new discovery . . .

The hills that flank our valley to the south are called Les Avant Monts, the Before Hills, and they're called that because as you travel northwards from the Mediterranean they're the first hills you have to climb before you reach the rolling uplands and mountains of the Massif Central. Here and there the southern, sun-kissed limestone slopes of the Avant Monts are scored with deep river-cut canyons. At the meeting point of two rivers that are now mostly subterranean, the Brian and the Cesse, there's a giant cliff-girt spur, and at some time in the remote past someone must have said Allez, this is just the place to build a village, because no enemy could ever scale those cliffs, and if they ever tried we could just shove them off into the ravine below and bon débarras, good riddance. Nobody would hear the splash because there's no surface water in the rivers, except in rare times of spate.

So they built a village, fortified the narrow neck of land joining the spur to the hill behind and sat pretty for hundreds of years. There was a problem with water, but they found wells, admittedly by digging further into the canyon base at the cliff-foot until they came to permanent river water. The most reliable well they called San Rustic, Saint Rustique in modern French. They fortified and covered the rock-hewn steps leading down from the heights.

They called their village Menerba. Nowadays it's called Minerve. It's given its name to the surrounding region and the often first-rate wines produced there: Minervois.

As you near Minerve your attention's drawn to a curious structure perched close to the edge of the gorge facing the village. At first sight it might be a crane or drilling rig. You may be none the wiser until you've followed signs in the village saying Remparts - i.e. ramparts, but you've guessed that already - until you've followed zig-zag paths and modern iron stairways down to the dry bed of the gorge, passing the St Rustique well-head on the way, until you've clambered up narrow paths cut into the rock on the other side. And there it is, a massive wooden structure. Suddenly it becomes clear: it's a replica of a medieval siege-engine, a machine that could hurl rocks, powered by the applied force of gravity. It even has a name: La Malvoisine, the bad neighbour, the neighbour from hell, if you like. To your surprise it appears to be in working order, and yet there's something not quite right about it, something that for the moment you can't quite fathom . . .

In fact this replica commemorates certain desperate events nearly 800 years ago, in 1210. The previous summer had seen the start of a Pope-approved crusade, not to regain anything in the Holy Land but to exterminate a harmless but heretic southern French sect later called the Cathars. This crusade was as probably as much to do with capturing Cathar lands for the French crown as imposing Catholic orthodoxy, but participants were promised rewards of captured land and the wiping clean of their sins from the slate. The town of Béziers was sacked, Narbonne and the walled city of Carcassonne fell. A well-connected thug called Simon de Montfort took charge (whose son, also Simon, became Earl of Leicester in Henry VI's England and founded the first English parliament) with a brief to root out all remaining centres of Catharism.

Up in the hills Minerve stood out, secure on its cliff-top perch. Simon de Montfort arrived, saw the natural strength of its defences, abandoned any idea of direct attack and settled down to beseige the village. The summer of 1210 was long and hot, supplies dwindled, but as long as the wells had water in them the Cathar villagers thought they could hold out until winter and the end of campaigning.

With immense labour Simon de Montfort installed a catapult on the cliff facing the village, one that could hopefully batter down the defences. His catapult, or sling, consisted of a main beam the size of a telegraph pole, a wooden box capable of holding at least a ton of stones, a massive frame to prevent recoil movement on the ground, plus ropes, pivots, winding gear - and ten horses and a hundred men to work it. Fire was slow: two shots an hour was considered quick.

As June passed into July Simon de Montfort concentrated his fire on the one remaining well, St Rustique. Some accurate boulders from La Malvoisine smashed the access, and the parched population gave in. 140 Cathars chose the flames rather than recant. There's a memorial to their martyrdom in the village.

But that replica: I looked at it hard and long, saying to myself yes, this ought to work: if you filled the counterweight box with stones and roped it to the short end of the pivoted pole, if your team of horses then hauled the long end down, so that the counterweight rose until the end of the pole touched the ground, if you firmly anchored the end of the pole to the ground while you unharnessed the horses and led them away, if you then rolled a massive boulder into a sling several oxhides thick and attached it to the long end (are you still with me?), then if you released the anchor the counterweight would fall, the pole would shoot upwards so violently that the boulder would be slung . . . where?  

Well, according to my reckoning, away from the village, in the opposite direction, into vineyards and rocky scrub of juniper, cypress and wild almond trees. Of course, that's it: why didn't I see it before? They've installed La Malvoisine the wrong way round. Deliberately. Just in case any latter-day Simon de Montfort decided to have a crack at reducing Minerve to a heap of rubble. Clearly there is intelligent life beyond our valley.