The City is the historical nucleus of London. Today it is the world's primary financial district, a rigidly mono-functional part of London. It retains the structure - both urban and political - of a medieval citadel, unaccountable and closed to exterior. This project proposes a radical change of program: by adding a whole new landscape of housing spaces on top of the existing offices, the City's contradictions are brought to light, and its anomalies can be addressed. The approach is at the same time conceptual and practical: the design is a straight answer to the challenges of building above an existing, very dense, urban fabric. The project's focus is not on architectural form; instead, it aims at showing that architecture is a way to propose new and unthought-of possibilities for urban transformation.