Archaeological sites of national importance are given legal protection by being placed on a 'Schedule' of monuments.In Wales there are over 4000 examples of Scheduled Monuments, which include Roman remains, burial mounds, castles, bridges, earthworks, the remains of deserted villages, industrial sites and 20th century military complexes etc. Scheduled Monuments cannot include in use ecclesiastical buildings or monuments occupied as a dwelling (other than by a Caretaker) and unlike Listed Buildings they are not assigned grades. Sites of Special Scientific Interest (SSSIs) cover a wide range of habitats from small fens, bogs and riverside meadows to sand dunes, woodlands and vast tracks of uplands.