The rock strata on which Dorking sits, belong primarily to the Lower Greensand Group. This group is multilayered and includes the sandy Hythe Beds, the clayey Sandgate Beds and the quartz-rich Folkestone Beds. The lower greensand was deposited in the early Cretaceous, most likely in a shallow sea with low oxygen levels. Over the subsequent 50 million years, other strata were deposited on top of the Lower Greensand, including Gault clay, Upper Greensand and the chalk of the North and South Downs.

Following the Cretaceous, the sea covering the south of England began to retreat and the land was pushed higher. The Weald (the area covering modern-day south Surrey, south Kent, north Sussex and east Hampshire) was lifted by the same geological processes that created the Alps, resulting in an anticline which stretched across the English Channel to the Artois region of northern France. Initially an island, this dome-like structure was drained by the ancestors of the rivers which today cut through the North and South Downs, including the Mole. The dome was eroded away over the course of the Cenozoic, exposing the strata beneath and resulting in the escarpments of the Downs and the Greensand Ridge.

Dorking is in central Surrey, about 21 mi (34 km) south of London and 10 mi (16 km) east of Guildford. It is close to the intersection of two valleys – the north-south Mole Gap (where the River Mole cuts through the North Downs) and the west–east Vale of Holmesdale (a narrow strip of low-lying land between the North Downs and the Greensand Ridge). The highest point in the town is the Glory Wood, south east of the centre, where the summit (137 m (449 ft)) is marked by a Bronze Age bowl barrow.

The basic plan of the town centre has not changed since medieval times (and may be Anglo-Saxon in origin). The main streets (the High Street, West Street and South Street) meet at Pump Corner, forming a ” Y ” shape. Together, West Street and the High Street run approximately west–east, paralleling the Pipp Brook, a tributary of the Mole, which runs to the north of the centre.