Old building in the woods in the castle grounds
Introduction
The photograph on this page of Old building in the woods in the castle grounds by Elliott Simpson as part of the Geograph project.
The Geograph project started in 2005 with the aim of publishing, organising and preserving representative images for every square kilometre of Great Britain, Ireland and the Isle of Man.
There are currently over 7.5m images from over 14,400 individuals and you can help contribute to the project by visiting https://www.geograph.org.uk

Image: © Elliott Simpson Taken: 12 Jun 2010
I am guessing that this is / was an ice house for storing ice collected in the winter to preserve food throughout the rest of the year.