At the north west corner of the restored Walled Garden the Shell Tower is a three storey, battlemented tower with single arched Gothic windows.

The lower rooms are decorated with shells laid in geometric patterns – presumably by the hand of a gifted lady of the house following the fashionable pastime of the 18th century. There are anecdotal tales of cart loads of shells being collected from Irish beaches to facilitate the inlay of such shell grottoes. The Shell Cottage at nearby Carton House under the design of Emily, Duchess of Leinster, is a wonderful example.

In the case of the Larchill Shell Tower, the shells appear to be mostly native varieties, many are cockles with some exotic exceptions such as conches – perhaps sourced via the trading connections of the 18th century Prentice family who created the Ferme Ornée at Larchill.