In the following years he organized and funded several expeditions to the Arctic and Africa and greatly expanded his private collection of specimens.

After his father died in 1903, Alexander Koenig planned a natural history museum to present his private collection to the public.

After the outbreak of World War I in 1914, the uncompleted building was confiscated and used as a military hospital and later, until 1923, as barracks by the French occupying forces.

Alexander Koenig, who had lost most of his fortune in the aftermath of the war, donated the museum and his private collection to the German government in 1929.

It shows complex ecological systems through dioramas of the African Savannah, a tropical rain forests, the polar regions, deserts and Central Europe.

The main building of the Museum Koenig houses the public exhibition and features a large central hall crowned by a glass roof.

He donated the house to his son in 1884 after Alexander Koenig received his doctoral degree and married Margarethe Westphal.

The building is named after Clas Michael Naumann, professor of zoology at the University of Bonn and former director of the museum.