castle vs Buckingham Palace

castle and Buckingham Palace both are nouns.

Word	Noun	Adjective	Verb	Adverb
castle	Yes	No	Yes	No
Buckingham Palace	Yes	No	No	No

castle (noun)	Buckingham Palace (noun)
interchanging the positions of the king and a rook	the London residence of the British sovereign
a large building formerly occupied by a ruler and fortified against attack
(chess) the piece that can move any number of unoccupied squares in a direction parallel to the sides of the chessboard
a large and stately mansion

castle (verb)	Buckingham Palace (verb)
move the king two squares toward a rook and in the same move the rook to the square next past the king