This article examines a document in the Spanish National Archive at Simancas, which entails a list of urban reform projects for Madrid in its early years as both court and de facto capital of the Spanish Habsburg monarchy. Herein, the document is dated to 1565 and attributed to Francisco de Sotomayor, a corregidor, or royal governor of the city appointed by Philip II. Sotomayor’s report on urban reforms was informed by years of service in Madrid both in government and in the royal works. It is the first surviving example of an effort at concerted town planning in Madrid, and one of the rare examples of such for sixteenth-century Spain in general. This article surveys the contents of the report within the context of evolving principles about Renaissance urbanism and also highlights the importance of public architecture for early modern cities. Sotomayor’s report emerges as one of the earliest catalysts for Madrid’s remarkable transformation from peripheral town to imperial metropolis.