 Hacquet was a fervent collector.In Ljubljana he operated a natural history cabinet (), which was appreciated throughout Europe and was visited by the highest nobility, including the Holy Roman Emperor, Joseph II, the Russian grand duke Paul and Pope Pius VI, as well as by famous naturalists, such as and .It included a number of minerals, including specimens of mercury from the Idrija mine, a "herbarium vivum" with over 4,000 specimens of Carniolan and foreign plants, a smaller number of animal specimens, a natural history and medical library, and an anatomical theatre.