peer reviewed ; The idea of compact city encourages a sustainable future in urban planning. Haphazard urban development affects the agricultural landscape of a country, degrades environmental qualities or leads to habitat fragmentation. Urban densification or development in already existing built up areas can help control such adversities. Addressing these challenges through the lens of compact city principles presents an intriguing avenue for sustainable urban development. Our study presents a theoretical framework as a solution to understand, analyze and implement urban densification in three provinces of Belgium: Brussels, Flemish Brabant, and Wallonia Brabant. Additionally, it talks about the future work based on regional planning scenarios for efficient land take. We use urban built up maps for three years 2000, 2010, and 2020 and then classified them into three density classes of 1 (low density built up), 2 (medium density built up), and 3 (high density built up). Using a genetic algorithm well known for its advanced single objective functionality, we optimized the neighborhood parameters for each density class built up. These are used in modelling urban densification from classes 1-2 and classes 2-3, using a multinomial logistic based cellular automata. Our findings show that while Brussels experiences high density with 80% of the region covered with residential built up, Wallonia still undergoes fragmented growth or urban expansion. Thus, our study can help the urban planners, researchers and stakeholders propagate an idea of smart solutions towards city planning.