The path is so called as it connects the River Thames with the North Downs, the hill range which is to the south as far as the western border of Surrey.

The route starts at Kingston upon Thames town centre and finishes at Box Hill & Westhumble railway station.

The path follows as closely as possible the banks of the Hogsmill River through the urban fringes of Kingston passing Berrylands railway station.

After crossing the A240 near Tolworth centre the walk leaves the Hogsmill River and continues on a narrow green strip between houses and beside a stream to reach the Horton Country Park, Ewell.

The route then passes through the edge of Ashtead and then begins to climb up to the North Downs, crossing the M25 motorway and then following the ancient Stane Street Roman Road through Tyrrell's Wood and on over Mickleham Downs from where a trip to neighbouring Box Hill on the path to the south is recommended for those making the return journey by foot.