Zip Code: Head in the clouds

One of the pleasures of driving along South Africa's highways is the intriguing signposts that promise to lead to great stories.

There are places like Kuikendieffontein and Ystervarkfontein, or the suggestive Hotazel. One of my favourites is the mysterious Riviersonderend on the N2 between Caledon and Swellendam.

I discovered, after signing up for the Cape Canopy Tours zipline, that the valley we would be cruising above was the source of the Sonderend River. To me that revelation is like spotting a unicorn (or a Cape mountain leopard).

Canopy Tours operates ziplines across the country from Tsitsikamma to the Drakensberg and Magoebaskloof, but the Cape tour is different - the cables do not stretch through a canopy of trees, but between the ledges and cliffs of a mountain valley.

The company's Elgin head office is in the Unesco World Heritage site Hottentots Holland Nature Reserve, a 10-minute drive from Grabouw. From there we bundled into a 4x4 for the bumpy ride to the top of the mountain, climbing through stunning valleys of fynbos, high into intrepid hiker territory.

Wearing gloves reinforced with a huge pad of leather for braking and a harness attached to the cable at three points, I swung off the ledge and zig-zagged between platforms high above the Sonderend valley.

Riviersonderend is false advertising. I saw the end, and it was stunning. Clouds squeezed like sponges over the mountain tops. The kloof's dark pools and waterfalls signalled the river's source.

It is a surprisingly lush crevice of giant ferns and proteas often visible only through cloud .

A jackal buzzard kept us company, scanning the slopes for lunch. Up in the crags I felt like a pioneer. There's the sense that few others have discovered the river and the kloof. No litter, no "Felix wuz here" carved into the rocks.

The Cape canopy experience recently came second on Lonely Planet's ''New in Travel" list of the best activities in the world.

Even if you've done your fair share of sky-diving, scuba, bungee or para-gliding, a canopy tour is a different kind of experience.

At Elgin, they cater for ages five to 95 so it's an activity the whole family can enjoy.

The toughest physical requirement involves being able to pull down on the zipline cable to slow yourself as you approach a platform. It's the equivalent of hauling back on the leash of a strong dog.

Even if you struggle with that, the guides have other safety measures to slow you down and get you onto each platform safely. There's also an easy 1km hike at the end.

• Cost: R595. Take good shoes/boots and a warm top. Visit www.canopytour.co.za