Square is a demonstration project for the energy-optimised existing development of residential quarters. The project, located on the conversion area of the Benjamin Franklin Village, offers integrated solutions for CO2 reduction at the district level. The lighthouse project is intended to be a model for the overall development of the 144 ha conversion site. The building blocks of SQUARE are: a) Model testing and implementation of CO2 mitigation measures in building renovation using two reference buildings (including monitoring and cost-effectiveness studies) b) Energy Mobility Cube – Decentralised district garage concept with decentralised energy generation and electric motorised individual transport (MIV) c) zero-emission public transport in the neighbourhood through a battery-driven electric bus (inductive charge) d) networking of energy generation, storage systems and consumption into a smart grid