Beijing is a city with an architectural history of nearly 3000 years. The old city of Beijing, like most pre-modern cities, was once encircled by high walls. The imperial city within was crisscrossed by myriad of hutong(alleys) and jiedao(streets) arranged parallel and perpendicular to a south-north central axis, a network structure which in essence survives to this day. The houses and courtyards in hutong(alleys)s are mainly residential houses, which we call siheyuan(quadrangles). People in siheyuan lead a quiet agreeable life: they are surrounded by flowers in early spring; they enjoy the cool breeze on summer nights it is a mode of life that more and more people these days would like to return to.