The design for this building is based on an 18th-century sketch of a temple which may have once stood on the site. The design was developed into an elliptical plan, featuring 12 columns and a flint grotto at the base of a mound made of earth. The ellipsoidal plain tile roof is capped with a sphere and bold gadrooned ovolo moulding, which features are reminiscent of the garden buildings to be found at Stowe.