The Tomb of the Kings refers to an ancient tomb located in Arabasta's capital, Alubarna, wherein lies the tombs and graves of the past kings of Arabasta. It is also the location of the Arabastan Poneglyph.
Arabasta Poneglyph Chamber
The Arabasta Poneglyph Chamber is hidden underground, below the Tomb of the Kings. Access is through a secret staircase.
This is where the poneglyph that contains information on Pluton is located and has been protected by the royal family for generations, although they do not know much else about the poneglyph. Inside, there is a hidden panel that can be activated to make the room collapse. The final battle between Monkey D. Luffy and Crocodile also took place here.
The room was forced to collapse by Nefertari Cobra in an attempt to kill Crocodile. As the room is collapsed, the current condition of the chamber and whether or not it was rebuilt is unknown, although since poneglyphs are said to be indestructible, it is likely that at least that survived.