To ensure that the decorative materials are permanently fixed, the walls and ceilings of the Grotto were first sprayed with glass fibre. This was then cut away in manageable sections and taken to France, where the artist's assistants covered them with mosaics of mirrors and glass. Finished sections were brought back to Hannover, fixed to the walls and ceilings, and the polyester figures mounted on the new surface.

These stunning interiors are the result of two years of painstaking and costly work through to the opening on 29 March 2003; the Grotto will then be open throughout the summer season, April till October, during Grosser Garten opening times.