Indeed, one of the Hotel’s most illustrious guests was Pope Pius IX who stayed here in 1866 in order to bestow honour on the Mexican Empress Carlotta who preferred the ornate splendour of the Grand Hotel Plaza to the modest accommodations of the Vatican!
The public rooms at the Grand Hotel Plaza, spacious, ornate with enormous crystal chandeliers, stained glass skylights were the perfect setting for important meetings between noble families, businessmen and politicians.

Among some of the most important historical events to have taken place here were the preliminary meetings between European member states who came to Rome for the European Treaty Conference on a Single European Market in 1957.