Rafting on the Dora Baltea river in Italy's Aosta Valley is the closest nature gets to a rollercoaster ride. In the care of an expert team of three, you go along a calm-ish, straight stretch and then suddenly drop down and are rocked back and forth for what seems like an age. In late spring, melting water from the mountains gushes down steep slopes restricted by impenetrable walls of rock on each side, causing our light dinghy to travel in a fast and furious fashion.
When we'd decided to visit this most northern region of Italy, active sports were not uppermost in my mind. But this Alpine landscape demands that you interact with it. Over the course of six days we – two adults and four children aged between seven and 11 – rafted, rock-climbed, and mountain-biked; we walked, trekked and zip-wired.
The Aosta Valley is Italy's least populated and most mountainous region. Surrounding it is a line up of genuine A-list peaks: Mont Blanc, the Matterhorn, Monte Rosa and the Gran Paradiso. To the west lies France, to the north Switzerland, and to the south and east the Italian region of Piedmont. It's a fusion of geological extremities and Alpine history, an area where three different countries and cultures converge.
Despite its mountainous location, the Aosta Valley is also very accessible: a two-hour drive from Geneva airport via the Mont Blanc tunnel or an even shorter drive from Turin or Milan. During the winter the Aosta Valley is all about skiing and the side-industries that go with it. The big hotels, chalet estates, bars and restaurants converge at hubs such as Cervinia and Courmayeur. But during the summer the focus is on walking and hiking.
Our week began in the town of Cogne, in the valley of the same name – a place that feels like the most benign of time warps. Cogne borders the spectacular Gran Paradiso Park, named after the mountain dominating it. For 150 years, remarkably forward-thinking legislation has protected this stunning expanse of mountain, meadow, forests and rivers. The area was originally declared a royal hunting reserve in 1856 in an attempt to protect a species of mountain goat, the ibex.
It might seem a drastic measure in the name of goats, but it's one that worked: the Savoy dynasty looked after the area well. They handed over their hunting estate in 1920 to the Italian government, who designated the district as the nation's first national park.
To this day the animals – chamois, marmots and eagles, as well as those indulged ibex – are still treasured. Our guide, Lilliana, was intent on showing us as many mountain species as possible. She took us on a trek passing abandoned mountain farmhouses that were gently (and picturesquely) decaying. They remain unmodernised because of strict laws restricting building work within the park. Even huge trees, victims of winter avalanches, were left to rot exactly where they had fallen.
While in Cogne we stayed in the convivial family-run Alpine hotel, the Bellevue. Built in the 1920s, it stands in splendid isolation in the middle of its own meadow, while all other hotels and guest houses, as well as shops and restaurants, are confined to the opposite side of Cogne's main street.
After three nights here we hit the big smoke: the town of Aosta, population 35,000 – which is as metropolitan as it gets in this valley. Founded by the Romans, Aosta has a pretty main square, and some good (and reasonably priced) restaurants. If you're keen to put together a picnic, there are delicatessens bursting with delicious local produce.
We based ourselves in Aosta for the rest of the week's activities. The highlight was an eight-mile "mini-trek" through the Great St Bernard Valley. There are two routes into the heart of this valley: an easy-to-navigate gravel path alongside a reservoir, or a more challenging path through woods, across streams, into meadows, and past mounds of melting snow. We opted for the latter – which left us with hearty appetites for a tasty lunch of polenta and goulash at the Rifugio Prarayer. This mountain cabin has a smallish restaurant, a bar, and sleeping accommodation for the scores of walkers passing through the Aosta Valley on the Matterhorn Tour (a gruelling 90-mile trek in the shadow of some of the greatest peaks in the Alps).
What really tested family fitness levels on this holiday was an afternoon spent mountain biking. We started and finished in the village of Planpincieux, in Val Ferret, with a cycling route that included a few steep climbs, a bumpy ride along a river path, a stretch along a seemingly car-free road and several glances from bemused anglers as our mixed-ability group navigated hired bikes through this scenically stunning valley.
We also attempted rock climbing on fixed ropes. With the help and coaxing of our guide Alessandro, we all managed to climb a couple of impressive rock faces and to abseil down. Maybe it was the bright sunshine that day, or the sense of achievement, or perhaps it was the endorphin high brought on by exercise and extreme sports, but this was a true moment of "family bonding".
For a less physically demanding day, we drove to Courmayeur and let a cable car – the Funivie Monte Bianco – take us up close to the summit of western Europe's highest mountain, Mont Blanc. When you reach Punta Helbronner at 11,358ft, the first thing that hits you as you step onto the viewing platform is the bitter cold. Then, if visibility permits, a multi-dimensional experience awaits as a collection of peaks come into view: Mont Blanc and – at the other end of the valley – the Matterhorn, Monte Rosa and Gran Paradiso.
From here you could continue over the French border to Chamonix, on Europe's highest cable car, but instead we started heading back down and stopped for lunch at the mountain restaurant, the Pavillon. Here we feasted on local specialities, from fontina cheese to chestnuts in honey.
But splendid though the food is, the real attraction of this tiny enclave at Italy's northern limit is the scenery. From peak to trough, wheels to white-water, the Aosta Valley reinvents the Alps as your family's own adventure playground.
The best gateways are the airports of Turin, Milan Malpensa and Geneva, all of which have low-cost links from the UK. By rail, the journey from London St Pancras takes as little as 11 hours.
Siobhan Mulholland and her family stayed at Hotel Bellevue (00 39 0165 74825; www.hotelbellevue.it) in Cogne. Doubles from €170 including breakfast, with a minimum stay of three nights.
In Aosta they stayed at the Hotel Milleluci (00 39 0165 235278; www.hotelmilleluci.com). Doubles from €150 with breakfast.
Mont Blanc cable car ( www.montebianco.com) costs €35 return to Punta Helbronner). Rafting costs €40 per person through Valtravel (00 39 0165 610434; www.valtravel.it). Three days' mountain-biking costs €85 per person through Bugella Welcome (00 39 335 574 4184; www.biellawelcome.com). Climbing and guides can be arranged via Cogne tourist office (00 39 0165 74835; www.cogne.org)
Rifugio Prarayer, Grand Saint Bernard Valley (00 39 0165 730922; www.rifugio-prarayer.it); Restaurant Pavillon, Mont Blanc (00 39 0165 844090).