Cool city design addresses urban heat island effect through innovative materials & design strategies. Cool pavements reduce surface temperatures by 20-30°C, cool roof coatings reduce building temperatures by 5-10°C & energy demand by 20-30%, district cooling systems reduce energy demand by 40-50%, & urban forests reduce temperatures by 1-2°C. Global examples including Los Angeles, Phoenix, Copenhagen, Singapore, & Melbourne demonstrate cool city design's transformative potential.