On the reverse of a study of a horse’s leg for his late equestrian monument (see eg. RCIN 912342, 912359, 912360), Leonardo has depicted a vast rectangular palace of three storeys, with square towers or pavilions at each corner and in the middle of each side. Bridges to either side of the palace, terracing down from the long flank, and a foreground that slopes and tapers towards us, all seem to indicate the palace was intended for a long, narrow river island. This topography corresponds with that of the island at Amboise (the Île St-Jean or Île d’Or), which to this day is reached from either bank by twin bridges at the south-western end of the island.

Around the same time Leonardo drew a simplified map of the island, with bridges at the same points, to study the currents in the Loire (Codex Arundel, fol. 269r). There is no indication of a projected palace on that map, and the focus of Leonardo’s architectural activity in France was at Romorantin, 30 miles (50 km) to the east. But so well does the topography of this sketch correspond with Amboise that Leonardo must have envisaged a grand new palace on the island, to supersede the jumble of buildings – some of them very recent – of the castle at Amboise, as seen in RCIN 912727.

Text adapted from Leonardo da Vinci: A life in drawing, London, 2018