长城在北京城外的北面.
to the+方位名词+of...指互不接壤并互不管辖的两个地区.
例:Japan is to the east of China.日本在中国以东.(不接壤)
in the +方位名词+of...指在某一范围内的地区.
例:Beijing is in the north of China.北京在中国的北部.(在内部)
on the+方位名词+of...指相互接壤并互不管辖的两个地区
例:The Pacific is on the east of China.太平洋在中国的东面.(接壤)