There are many synonyms for the term "royal residence" which implies a grand and extravagant residence for the royal family. The most common synonyms include "palace" which is a grand, luxurious, and stately building, or "château" which is a castle or palatial country house. Other synonymous words include "mansion", "manor", or "estate" which signify a large and impressive home. Another word that can be used is "fortress", a word that shows the strength and power of the royal family. Alternatively, the term "seat" or "residence" can be used to refer to the royal palace or domain. Overall, there are numerous synonyms for "royal residence" that all signify the grandeur and immensity of a place where royalty resides.