Cities in Mediterranean climates face challenges due to climate change and energy scarcity. Urban areas experience higher temperatures than rural areas, known as the urban heat island effect. This study looked at how city layout affects heat islands and energy use. In Rome and Barcelona, streets are hotter than rooftops, with temperatures over 4 ºC higher. Different city layouts affect heat islands differently: more horizontal surfaces make winter hotter, while more vertical surfaces make summer hotter. The study used computer models to analyze these effects and found that blocking sunlight and urban layout both impact energy use in cities.