OCTOPLUS is a design for the expansion of the Heilig Kreuz College. Meeting the necessary requirements meant renovating the main building and planning a new element to match the current buildings on the site. Such a measure serves to architecturally connect buildings of different styles and eras. The general organization of the building and the layout of the rooms will be completely changed so that the building components achieve a synergy effect together and can still be used independently of each other. The hollow concrete slabs are an efficient technique for reducing CO2 emissions, the dead weight by 35% and the foundation load by 15%.