Grade I listed buildings in Caerphilly County Borough
In the United Kingdom, the term listed building refers to a building or other structure officially designated as being of special architectural, historical, or cultural significance; Grade I structures are those considered to be "buildings of exceptional interest". Listing was begun by a provision in the Town and Country Planning Act 1947.
Source: Wikipedia — Grade I listed buildings in Caerphilly County Borough (CC BY-SA 4.0)