An oculus (or in French oeil-de-boeuf - bull's eye) is a circular architectural feature usually in the centre of a wall or dome. Such a feature was often found in Byzantine or Neoclassical architecture.

This would make a wonderful garden feature perhaps a window onto another part of the garden.

Height: 1.32m (52in)
Width: 1.3m (51in)
Hole diameter: 75cm (29.5in)