 Crossing the Blue Mountains was particularly challenging due to the mistaken idea that the creeks should be followed rather than the ridges, and almost impenetrable, labyrinthine, sandstone mountains.Although the most daunting obstacle to western expansion of the colony, the Blue Mountains actually lie to the east of the watershed that divides the Hawkesbury-Nepean system and the Murray-Darling system, the true Great Dividing Range.The watershed in this area lies to the west of Lithgow, passing near the locality of Mt Lambie and village of Capertee.