At the building scale, design has traditionally been carefully adapted to local climate conditions, in order to reduce undesirable influences and exploit the desirable aspects of the climate. In countries with strong sun and high temperatures, city structure features shady narrow streets and buildings with thick walls and small openings. Colder climates call for a different strategy. In Scandinavia where the angle of sunlight is low, frequent winds bring warm air overland from the Atlantic Ocean, one of the reasons it has been possible to live and grow crops in this region. The old cities in the region have carefully adapted to the low angle of sunlight and almost constant wind. Buildings, typically between two and three stories high with slanted roofs, are clustered. Streets, squares and gardens are small and the many trees between buildings provide shade and shelter.