Totternhoe Knolls
Part of the site was formerly a quarry where Totternhoe Stone, a strong type of chalk that was used in Westminster Abbey, was mined. This part is now grassland with a rich variety of plant species, including some that are now rare; these are characteristic species of chalk downland and include kidney vetch, horseshoe vetch, large thyme, squinancywort, autumn gentian, clustered bellflower, sainfoin and dwarf thistle. Orchids that grow here include common spotted orchid, Herminium monorchis Musk orchid, Orchis anthropophora Man orchid, bee orchid and twayblade . There are a wide variety of invertebrates, including butterflies such as the common blue, the chalkhill blue, and the scarce small blue and Duke of Burgundy fritillary.
Totternhoe Castle was probably built in the late eleventh century. Only the earthworks survive, with a mound five metres tall and 40 metres wide. It is unusual in having three baileys.
There is access from the National Trust car park off Castle Hill Road.