What is the fine-grained topic of the following text: Two miles from Stamford, this interesting 15th Century National Trust building contains a museum of local bygones and an extensive exhibition on the mining and preparation of Collyweston slates – an ancient and unique local industry that flourished until the 1950s. Only return the topic.
Collyweston slates mining and preparation exhibition in a 15th Century National Trust building near Stamford.