请用英语描述“福建土楼”的建筑特点和历史意义，且每段10个词以内，包含“earth buildings”。
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Earth buildings in Fujian are circular structures made of rammed earth. Historically, they served as strongholds against invaders. These earth buildings were homes to extended families. Their design maximized space and defensive capabilities. Earth buildings showcased traditional Chinese architectural ingenuity. Constructed in Fujian during the Ming and Qing dynasties. Earth buildings are now UNESCO World Heritage Sites. These structures signify communal living and cultural unity. Their enduring design has captured global attention.
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