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learning this and other similar sciences, surrounded by the best teachers and ensuring that their heirs were instructed in these matters, which were seen as very important for future governance.

The manuscript plans in the Swedish Military Archives include a drawing (44) probably made by Prince Baltasar Charles two years before he died. The heir’s enthusiasm for cartography is well known, as is the suggestion made by Saavedra Fajardo to Philip IV concerning the suitability and pertinence of creating a map room for the prince’s exclusive use. That Baltasar Charles did learn is evident from an engraving in the Stockholm Archives containing quite an explicit text which, translated, reads: “Floor plan of the Casa de Campo fort drawn by his Royal Highness our Prince and Lord to apply what he has learned of military architecture, for both attack and defence. In Madrid in the year 1644” (45). So the idea behind this engraving was to pay tribute to a young prince by showing his ability in the art of cartographic representation. And it is not surprising, therefore, that the two drawings were, for sentimental reasons, part of the collection of the Marquis of Heliche –the owner of most of the cartographic documents that Johan Gabriel Sparwenfeld took to Sweden–, with whom Prince Baltasar Charles had a close lifelong relationship.

This cartography, which was considered to be official, was kept and included in the category of “arcana imperii” –State secrets– and was therefore never printed, as was the custom with any document of this nature that was even slightly related to strategic issues pertaining to the Kingdom or Empire. This practice was instated by the Catholic monarchs when they created what was called the Padrón Real or