南临“不尽浪滔滔”的渤海,北依绵延数千里的长城,雄关耸立,虎踞龙盘,这就是被称为“两京锁钥无双地”的天下第一关——山海关。山海关位于东经119°45′,恰处于北纬40°线上,属大陆性季风气侯,但受海洋影响很大,气侯温和湿润,年平均气温10.1℃,既使在最炎热的7月份平均气温才24.5℃左右,年平均降水量为665毫米,年平均相对湿度60％,海滨地带夏日凉爽,是避暑的好地方。发源于长城以北青龙县老刘家岭东南麓的石河,就流经山海关附近而后注入渤海。该河长67.5公里,流域面积600平方公里,山区植被覆盖率50～60％,水土流失不甚严重。在该 South of the “endless waves” of the Bohai Sea, north by the Great Wall stretches for thousands of miles, hung off, Hu Ju Longpan, which is known as the “two key to Beijing unparalleled” the best off in the world - Shanhaiguan. Shanhaiguan is located at 119 ° 45 ’east longitude and just at 40 ° north latitude. It belongs to the continental monsoon climate. However, it is greatly affected by the oceans. Its climate is mild and humid with an annual average temperature of 10.1 ℃. Even in the hottest July, The temperature is only about 24.5 ℃, the average annual rainfall of 665 mm, the average annual relative humidity of 60%, the summer cool summer beach is a good place for summer. Originated in the north of the Great Wall north of Liujia Ling Qinglong County Stone River, flows through the Shanhaiguan and then injected into the Bohai Sea. The river is 67.5 kilometers long, with an area of ​​600 square kilometers and a vegetation coverage of 50-60% in mountainous areas. Soil erosion is not serious. In that