[2] In his early stage he was one of the major architects who introduced the Vienna Secession in Croatian architecture.
During that phase he created several impressive designs, such as a house Rado at Strossmayer Square 7 in 1897, sanatorium in Klaićeva Street known for its V-based ground plan in 1908, and the building of the deanery and the institute of pathology at the Medical Faculty of Šalata in 1912.
[2][8] During the Interwar period, Fischer designed in the spirit of late modernism, historicism and, modestism.
His greatest achievements are the forestry Academy building in Mažuranić Square 5 in 1920, the head office of City Savings Bank of Zagreb on Ban Jelačić Square in 1922–1925 (upgraded in 1931), and modern house Arko at Dolac Market.
Recent research discovered a number of architectural designs that were previously not attributed to him, most notably the building of the Croatian Parliament in the St. Mark's Square.