The Blue Mountains are so named because, from Sydney, they look blue. They are clad in vast forests of eucalypts (commonly called gum trees), which in the hot sun discharge a fine mist of eucalyptus oil from their leaves. The mist refracts light, which makes the haze look blue at a distance. That same oil makes the Australian bush as volatile as a pine forest in a bush (forest) fire. The vapour explodes, causing the fire to race through the canopy.

They are part of the Great Dividing Range, which stretches from Gippsland region of Victoria in the south to the tropical rainforests of north Queensland.

Interestingly, the Blue Mountains are millions of years older than the Himalayas.

The Blue Mountains were once thought of as the barrier to freedom, with many early settlers believing China was on the other side. Peaking at about 1100 metres, they proved a heartbreaking challenge until they were conquered by a trio of explorers - Gregory Blaxland, William Lawson and Charles Wentworth in 1813. They and four men hacked through dense bush for 18 days to find a route.

The first road was cut into the Blue Mountains by William Cox using a team of 30 convicts and eight guards. Starting at Emu Plains at the foothills in July 1814, they cut an incredible 47 miles to Mount York (past the highest point of the mountains at Mount Victoria - 1064 metres) in just four months.

The rock strata which forms the dissected plateau of the Blue Mountains are the result of millions of years of deposition of sands and silts. Huge river systems from the north west and later from the south west dumped vast quantities of material over this area.

The extensive coal and shale deposits were formed around 245 to 290 million years ago. The swamps supported a large Glossopterid forest, which was eventually covered by the sands and silts.