Further along , on Bebelplatz , the Berlin State Opera , No. 7 , colloquially called `` Lindenoper '' , St. Hedwig 's Cathedral and the `` Altes Palais '' , No. 9 , the favourite residence of Emperor Wilhelm I ; next on the north side are the main building of the Humboldt University , No. 6 , and House I of the Berlin State Library , No. 8 .
Furthermore on Bebelplatz the Berlin State Opera ( No. 7 ) , coloquially called `` Lindenoper '' , St. Hedwig 's Cathedral and the `` Altes Palais '' ( No. 9 ) , favoured residence of Emperor Wilhelm I ; in the north the main building of the Humboldt University ( No. 6 ) and House I of the Berlin State Library ( No. 8 ) .