This chapter is an introduction to the complex subject of medieval London. It proposes to maintain, where possible, an almost aerial viewpoint and describes some of the main features of the development of domestic buildings in London from the 13th to the 16th century. The chapter provides a brief survey of the most useful sources for study of medieval and Tudor London buildings, and then suggests some of the significant developments in domestic architecture and planning in these centuries. The main sources of domestic building in this period are the surviving historic fragments, the results of archaeological excavation, and documentary evidence. Pre-Fire domestic buildings have been excavated on a number of sites, all since the War. The development of housing in London, as in other medieval cities, was subject to many gradual developments and changes within a densely-populated urban topography which was already finely structured by the early medieval period.