The hotel continued to expand, and on December 15, 1886, Speilsalen (the Mirror Room) opened its doors. For the first time, people could dine to music played by the restaurant orchestra.
Academics and foreign diplomats gathered here for lunch. The most elegant reception room in Norway opened in 1894 in the presence of playwright Henrik Ibsen. The Rococo Room extended over two floors and was elaborately decorated with murals by Krogh on the walls and ceiling. It provided an elegant setting for countless balls, artistic exhibitions and shows, and Petra Sand's charity soirees. Last but not least, "The Ball Society", under the patronage of Queen Maud and King Haakon, held their arrangements here.
When Roald Amundsen returned to Oslo after his successful expedition to the South Pole in 1912, a banquet was held in his honor at the Grand Hotel.