[1][2] Together with the Czech Josip Pospišil and the Austrian Ernst Lichtblau, who had all studied at the Art Academy in Vienna with Karl von Hasenauer and Otto Wagner, Tönnies is considered one of the proponents of the "Bosnian style" as a step towards architectural modernism in Bosnia and Herzegovina, as opposed to Moorish Revival style[3] Rudolf Tönnies studied construction and civil engineering and worked for the Croatian government in Zagreb, then as lead architect for the Government of Bosnia and Herzegovina in Sarajevo, where he left among the most notable residential and mixed buildings in Vienna Secession style in town.
[4] In 1918 he returned to Ljubljana, obtained a trade concession (building master) and joined his brothers.
In Ljubljana he built around 1923 the Credit Bank (today the seat of the National Bank) and at the same time the Ljubljana yard (headquarters of Railway Transport Company).
[2] In 1898 he married Paula Faller (Ivanec, Varaždin, 22 August 1864); they had a daughter, Frigga Tönnies.
[5] Tönnies also contributed to the Bosnian style in architecture, which can be compared with Scandinavian National Romanticism.