Casa Botter (Botter Apartmanı) (1900–1901), a seven-story workshop and residence building in İstiklâl Avenue in Beyoğlu, which he designed for the sultan's Dutch fashion tailor M. Jean Botter, represents a turning point in D’Aronco's architecture. This Art Nouveau design in the avant-garde mood of the period compounded D’Aronco's already enviable reputation. While living in Graz at fourteen, he had also found the chance to follow the Austrian Secession more closely than most of his compatriots.