The Colo River is the wild neighbour of the Hawkesbury. It rises in the rugged sandstone country of Wollemi National Park, one of the largest wilderness areas in New South Wales, and it runs through gorges that no road has ever reached before joining the Hawkesbury near the point where the valley opens out. Where the road meets it, the river is calm, broad and green, edged with she-oaks and tall river gums, and the banks are soft with sand.
The region is the western fringe of Sydney's hinterland, about an hour from the city, yet it has an end-of-the-line character. Small farms and weekenders are spread along the river flats, with paddocks, horses and the occasional old boat shed, and the road bends and dips through cuttings in orange rock. The land belongs historically to the Darug and Darkinjung peoples, who lived and travelled along the river for thousands of years, and rock engravings and shelters are preserved in the wilderness.
For motorcyclists the surrounding roads are famous. The Putty Road, which runs north from the Hawkesbury toward Singleton, is the best known, a long, twisting route through forest and ridge that has been a rider's favourite since before anyone remembers. It is also one of the most heavily policed roads in the state, with frequent patrols and enforcement at weekends, and with a record of serious crashes that has led to lower limits and stern signs. Take it at a measured speed, enjoy the rhythm, and give the bends the respect they deserve. Surface condition varies, and gravel can wash across the road after rain.
The river is a cool place to take a break in summer, and a pull-off near the bridge gives access to the water for a paddle. Be careful with swimming, because the currents can be stronger than they look. Canoeists and kayakers use the river, and there are camping spots along the banks, though you should check which are open and whether permits are required. In the hot, dry months, bushfire danger can be extreme, and roads may close, so follow the local alerts.
East Kurrajong, about nine kilometres away, is small, and Richmond, about twenty kilometres, is the safest place to fill before the long run north. The Putty Road itself has very few services over its length, so a full tank is essential.