The Blue Mountains - so called because of the blue haze created by the eucalyptus oil in the air above the mountain gum forests - are a natural wonderland.

From lookouts on the edges of the Blue Mountains National Park, cliffs fall away towards blue ridges broken by waterfalls that plunge into bowls of gum trees or narrow ravines.

Ancient rock formations, such as the Three Sisters, The Ruined Castle and Pulpit Rock, stand out starkly against the blue of the sky, or poke up through mountain mists. You can abseil over roaring waterfalls, walk through canyons that have remained unchanged from the Jurassic era, paddle beneath glow-worm covered overhangs, stroll under groves of huge tree ferns, and swim in crystal-clear pools.

Each season brings an array of changing colours, as well as different activities. Spring brings strolls among wildflowers, and summer lazy days and cooling shadows. In autumn, the European trees that colour the historic towns turn red, and in winter there are wood fires and even the odd sprinkling of snow.

In Katoomba, gateway to the Blue Mountains, you can ride the Scenic Railway - the steepest incline railway in the world - or enjoy the breathtaking views from The Skyway, a gondola-style cable car.

Historic towns boast antique shops, art galleries, Victorian and Edwardian-style buildings and Devonshire teas with lashings of whipped cream. Outside, yellow-tailed black cockatoos, king parrots, crimson rosellas and gang gang cockatoos flutter around stately gardens.

More than three million people venture to the Blue Mountains National Park and World Heritage area each year. Some come to just stand and stare across its dramatic and uplifting landscape. But for thousands of fearless adventurers this is the place to mount a horse or don a wetsuit, a climbing harness or caving overalls for an exhilarating journey into the wild.

The World Heritage-listed park covers one million hectares. Half of it is wilderness, and within it are hundreds of kilometres of cliff faces to climb, chasms to rappel, canyons to negotiate, underground caves to explore, crystal streams to swim and deep valleys in which to ride.