公元前333年流传至今的长城，你知道她到底有多长?当时赵国为了防卫开始修筑长城，继后成风，齐、魏、燕…也跟着修筑长城自卫。
B-Time I-Time I-Time I-Time I-Time I-Time I-Time O O O O O B-Location I-Location O B-Person O O B-Location O O O O O O B-Time I-Time B-Location I-Location O O O O O O O O B-Thing I-Thing O O O O O O B-Location I-Location I-Location I-Location I-Location O O O O O O B-Thing I-Thing O O O