Billudden is the outermost part of Uppsalaåsen; here the esker forms a promontory into the sea before disappearing from sight underwater.

The nature reserve is characterised by the hilly form of the esker, which is still rising with as much as 70 centimetres (28 in) per century due to post-glacial rebound.

Areas of windblown sand and sparse Scots pine woods can also be found in the nature reserve.

The nature reserve furthermore contains the largest concentration of common sea buckthorn in Europe and several unusual fungi.

It lies next to a natural harbour which formed during the last ice age when an ice block of unusually large proportions melted here, creating a circular indent in the shoreline.