Blue space (also referred to as blue infrastructure) in urban planning and design comprises all the areas dominated by surface waterbodies or watercourses. In conjunction with greenspace (parks, gardens, etc. specifically: urban open space), it may help in reducing the risks of heat-related illness from high urban temperatures (urban heat island).Substantial urban waterbodies naturally exist as integral features of the geography of many cities because of their historical geopolitical significance, i.e. the River Thames in London.