This book is about the stone used to build the castles of Edward I in North West Wales. It provides a description of the available geological resources and the building materials used in the construction of Caernarfon, Conwy, Harlech and Beaumaris Castles. It takes a broad view of this subject, placing the stone used in the castles in the context of both earlier and later buildings across the region of study, from the Neolithic up until the present day. The book will serve as a useful source book for geologists, archaeologists, architects, representatives of the natural stone industry, historians and cultural heritage management professionals specifically and for academic and non-academic communities, travellers and tourism industry operators in general.