The Princely Apartments are shown with their original furniture dating from the latter part of the 18th century. In the 1780s Electoral Archbishop Friedrich Karl Joseph von Erthal (r. 1774–1802) had Johannisburg Palace modernized in the Neoclassical style by the architect Emanuel Joseph von Herigoyen (1746–1817) and the furnishings replaced.
The electoral apartments were originally on the first upper floor of the palace. After it was rebuilt, they were reconstructed on the second floor in a different sequence. The reconstruction was based on prewar photographs and original designs from the 18th century.