Geographical Information Systems (GIS) are becoming increasingly popular in historical research, especially in urban contexts. However, digitizing historical sources in a way that can be mapped using the Cartesian co-ordinate systems of a GIS is often challenging, especially so in the case of records pre-dating centralized property registers or street numbering. This article explores how the vernacular spatial descriptions used in several case-studies of documents from late medieval and early modern London can be translated and geocoded into GIS compatible co-ordinates in a sympathetic way. Translating this data from a historical spatial paradigm into a modern one unlocks a whole range of new insights into spatial patterns, networks and relationships which would not have been feasible to construct using traditional methods