Gustav Tönnies acquired quarries in Nabrežina, Repentabar and Momjan. He also founded the factory "Strojne Tovarne" in Livarne Šiška and a brickworks in Koseze (which had the first circular furnace). In 1871 he joined company with F. Dobner, formerly directors of the ironworks at Dvor at Žužemberk, and in addition to building locksmithing, he also established an iron foundry and machine workshop; In 1880 Dobner exited the company, and Tönnies remained the sole owner of the "Gustav Tönnies machine shop and iron foundry". In particular, he made machinery for the wood industry and crafts, vacuum cleaners, turbines and steam engines. In 1895, an earthquake struck Ljubljana and the Tönnies Company was a great asset to the rebuilding of the city supplying the much needed construction materials for the building projects in progress. This dedicated engineer received an award from Francis Joseph on the 600th anniversary of the accession of Carniola to the Habsburg Monarchy. At the time of his death in 1886, the Tönnies establishments employed 650 people. The Tönnies sons continued their father’s legacy and built the court palace; a town hall; a gymnasium; Maldika; the Catholic printing house (today the Faculty of Law); Jakopič’s pavilion in Tivoli; the Yugoslav Credit Bank (now the Bank of Slovenia); the main railway station in Ljubljana and many other buildings in Ljubljana. In addition to the construction work of Tönnies, they also had important achievements in mechanical engineering. The machinery developed included that what was used in forestry industry; wood processing; pumps and turbines; belt presses and the instruments for measuring earthquakes.