外地人到北京，印象最深的恐怕是北京的灰城灰瓦，且不说古朴的四合院，就连平安大道两侧也是一溜儿灰，再加上北京以往灰蒙蒙的天，大风起处漫天的尘土，灰色几乎成了冬日北京的代名词。然而，近几年人们惊喜地发现，北京正在悄悄地变化，绿色增加了，天变蓝了，水变清了，北 Foreigners to Beijing, I am afraid the deepest impression is Beijing’s gray-brick, and not to mention the simple courtyard, even on both sides of the Avenue of Peace is a slippery gray, together with Beijing in the past overcast gray sky, gale everywhere Dust, gray almost became synonymous with winter Beijing. However, in recent years, people were pleasantly surprised to find that Beijing is quietly changing. As the green color increases, the sky turns blue, the water becomes clear, and the north