未知{みち}の文明{ぶんめい}の遺跡{いせき}relic of an ancient civilization: 古代文明{こだい ぶんめい}の遺跡{いせき}relic of an early civilization: 古代文明{こだい ぶんめい}の遺物{いぶつ}traces of an ancient civilization: 古代文明{こだい ぶんめい}の跡