Among the most interesting rooms of the Grand Palace, I recommend the Chesma Hall, with 12 large paintings by the German, Jacob Philipp Hackert, of the Battle of Chesma, the extraordinary naval victory of the Russian-Turkish war.
Fun fact: In order to make the paintings of the battle of Chesma more realistic, Tsarina Catherine II blew up a frigate in the port of Livorno in Italy, so that the artist, who had never seen a naval battle, could draw inspiration from it.