A secret passageway into the palace vaults, a door, and a Magicked Stone to open the way.

The Royal Palace is an unrevisitable location within Rabanastre in Final Fantasy XII. The player can access it via a secret entrance in the Garamsythe Waterway, but it can never be visited again.

A short walk north from the center of Rabanastre will lead you to the gates of the royal palace. Before the war with Archadia, this magnificent structure was home to the Dalmascan royal family, and barracks to the order of knights that served them. It is currently employed as a living quarters and apartments by the recently appointed consul from Archadia. The palace itself was built several centuries ago and has since been home to many Dalmascan monarchs, King Raminas being the most recent. Numerous additions have been made to the palace over the course of its long history (the Royal City of Rabanastre having several times fallen under the control of foreign powers through invasion), but the overall bearing of its architecture is true to the original Galtean design. Within the palace are secret chambers containing documents and treasures belonging to the royal family. Few who live beyond the palace walls know how they may be found.
Sage Knowledge 41

The Cellars area has many treasures, but one of them is a forbidden chest (labeled in red) that, once claimed, prevents the player from obtaining the Zodiac Spear in Necrohol of Nabudis. When sneaking into the palace there are several chests in the Cellar. The forbidden one is among the two chests in the southeast corner. The forbidden chest contains an Elixir, while all the others have common items like Potions and Antidotes, so the player can easily reset the game if they take the wrong treasure.

The concept of forbidden chests was removed in the Zodiac versions.

No chests respawn in this location.