Around 1526, Emperor Charles V decided to build a new Renaissance palace in addition to the Nasrid palaces in the Alhambra of Granada, a monumental site currently included in the United Nations Educational, Scientific and Cultural Organisation (UNESCO) World Heritage List. In that period, a large floor plan, which is preserved today at the Library of the Royal Palace of Madrid, was drawn to represent the building and its surroundings. Although this anonymous drawing has attracted considerable historiographic interest, a study of the graphical aspects analysed here, namely, paper assemblage, drawing technique, representation system, metrology, graphical scale, dimensioning, and labelling, is lacking. To accomplish this analysis, the original document was carefully examined and digitalised with high definition. This process allowed a comprehensive graphic analysis, utilising other drawings from the same period as a comparative reference and studying for the first time the major characteristics of one of the most relevant architectural drawings of the 16th century.