The Malachite Room was part of the Winter Palace in Russia.
After Cousin Anastasia founded the Thirteen-Day Republic, she added polished sheets of malachite to the walls, with which one could see dark reflections of the whole room. It served as the center of power in the Thirteen-Day Republic, and while the Republic was allegedly built on principles of equality and solidarity it was very clearly Anastasia's room. (PROSE: The Book of the War)