Simplify the following text for a Grade 10 native English-speaking person.
Original: A rÃ th ( anglicised rath ) , was made of earth , caiseal ( northwestern Ireland , anglicised cashel ) and cathair ( southwestern Ireland ) were built of stone .
Simplified: They are found in Northern Europe , especially in Ireland . In Irish language sources they are known by a number of names : rÃ th ( anglicised rath ) , lios ( anglicised lis ) , caiseal ( anglicised cashel ) , cathair ( anglicised caher or cahir ) and dÃ n ( anglicised dun or doon ) .