What is the name given to Australia's most extensive mountain range system?

The peaks are called the three sisters I have visited on a wonderful trip to Australia from England :)

The three sisters overlook the megalong valley which is the second longest valley in the world, after the grand canyon.

Mrs T, 'The Three Sisters' are located Echo Point at Katoomba; on north escarpment of The Jamison Valley. All being only a part of Great Deviding Range; Running through States: Victoria, New South Wales n Queensland. Marvellous nature 👌

Latisha, no just The Three Sisters.

Latisha, that's just one partucular rock formation

I was told by locals it’s called 3 sisters mountain 🙂

highest point: Mount Kosciuszko, previously spelled Mount Kosciusko, is also mainland Australia's tallest mountain, at 2,228 metres above sea level. Wikipedia