In the 1700s, the palace was expanded by John Ernst, Count of Nassau-Weilburg, and his builder, Julius Ludwig Rothweil [de].

The buildings and gardens now belong to the Verwaltung der Staatlichen Schlösser und Gärten Hessen, and they can be visited as a museum on guided tours.

[2] In 1703, John Ernst, Count of Nassau-Weilburg, commissioned builder Julius Ludwig Rothweil [de] to expand the palace.

A combination of conservatory and ballroom, it has large windows on the inner, eastern side of the curve and trompe-l'œil tiles on the walls.

[4] At the south end of the Obere Orangerie,[4] the town hall (Rathaus) and church (Schlosskirche) were built, and the garden terraces (Schlossgarten) were installed.

[6] The Schlosskirche is regarded as one of Germany's most notable Protestant Baroque church buildings, along with St. Michaelis in Hamburg and the Dresden Frauenkirche.

[8] The fountains, gardens, and baths of the Baroque palace required an abundant water supply, and a new system had to be built.

[8] At the north end, Viehhof was heavily redeveloped, with the building of the Marstall (formal stables), the Prinzessenbau, and the Kabinettbau.

[3] The Prinzessenbau and Marstall are now the Schlosshotel ("Castle Hotel") and the Kabinettsbau and Reitbahn are now the Stadthalle (city event space).

[2] After World War II, it was managed by the Hessian administration, Verwaltung der Staatlichen Schlösser und Gärten Hessen [de], which is responsible for the preservation of the buildings and the gardens.