Medium-sized cities in Spain have undergone significant changes in their urban structure due to rapid growth and real-estate development since 1980. The once compact and dense city layouts have expanded outward, leading to sprawling and fragmented urban areas. This growth model is unsustainable and has resulted in a 50% increase in the number of medium-sized cities, a 109% increase in houses built, and an 87% increase in developed land. GIS technology was used to analyze these changes, confirming the significant transformation of urban forms in Spain. The current urbanization trend is not sustainable according to the 2030 city strategy.