Beethoven made the 4th floor of this house his residence from 1804 to 1814 (he apparently occupied around 80 places in his 35 years in Vienna, but thankfully not all of them are museums!) and during that time composed Symphonies 4, 5 and 7 and the opera Fidelio, among other works.
His two rooms (plus another two from a neighbouring apartment) have been converted into a museum, which is lightly filled with photos, articles and a handful of his personal belongings. The house is named after its long-time owner Josef Benedikt Freiherr von Pasqualati.