Between 1459 and 1474, the duke of Burgundy ordered the construction of an entirely new residence in Lille, known as Palais Rihour. It was Philip the Good’s most ambitious architectural project, which set new standards for the display of princely magnificence. Among the new architectural features were a regular plan, a long gallery, a square stair tower with straight flights, and brick-and-stone masonry. The design had a significant impact on the development of court architecture in fifteenth- and sixteenth-century Spain and northern Europe. Despite its importance, Rihour has received little scholarly attention, the major work by Max Bruchet being almost a century old. The study of Philip’s residence is hampered by the loss of most of the structure. Following damage by two major fires in the eighteenth century, the entire complex was demolished in the mid-nineteenth century and today only the chapel and the relocated monumental stair tower survive. However, extensive archival research allows for a detailed reconstruction of Rihour’s phases of construction. The exceptionally numerous surviving letters offer a rare insight into the planning process and reveal the close involvement of Philip (1396–1467), and later his son Charles the Bold (1433–77), in the construction. Both Valois princes were concerned with minute details, and their frequent changes of mind caused despair among the building’s administrators, the auditors of the Chambre des Comptes of Flanders. The administrators advocated a more pragmatic approach, proposing cheaper alternative solutions to balance cost with the speed of construction. The innovative design was thus also the product of compromise.