The castle is considered one of the best "examples of late 13th century and early 14th century military architecture in Europe," by UNESCO. It sits on the coast. The coast is made up of a lot of rocks, including grey sandstone and limestone. Most of the stone that the castle was built out of is from this stone. The sandstone used to make carvings was brought from the Creuddyn peninsula, Chester, and the Wirral. That sandstone had more colors than the grey sandstone that was local. It might have been chosen not only because it was easy to carve, but also because it was pretty.