Rubicon’s 20 ha of land is relatively flat, about 15–20 metres above sea level, surrounded by farmland and rural residential developments. Its underlying geology is Jurassic dolerite, overlain with Tertiary sand and sandy loam.
The landform undulates, with shallow ridges supporting well-drained sandy woodland. Between the ridges are shallow depressions, some of which fill with shallow water in winters with average rainfall. These depressions have humus rich soil, at least on the surface. Between these extremes of landform are areas of near-level ground where the soils become saturated in average winters, where small pools of surface water persists for a time after rainfall events.
The map below depicts the places where soils become waterlogged in an average winter, shown in pale blue, and the maximum extent of shallow pools in wet winters, shown in dark blue.