The Three Musketeers: The Queen's Diamonds filmed at La Granja de San Ildefonso. This summer palace, a miniature Versailles southeast of Segovia, hosts the final ball, where the queen has to don her diamonds. On screen it's Hotel de Ville.

Probable Named in published production coverage; the coordinate is the place itself, checked against a gazetteer.
Planning the trip? The Spain travel atlas covers money, language and getting around
Venture keeps every scene location on one map, sorted by how far you'd have to walk. Open it in La Granja de San Ildefonso and it tells you what was shot around you, how to get there, and whether you can actually go in.
Download Venture for iOS Android