After several fires before, in 1774, the three-wing annex was again destroyed by fire, with only the enclosure walls left standing. Duke Carl August convened a palace construction commission under the direction of Goethe.
In 1816, Clemens Wenzeslaus Coudray started planning the west wing; construction work on this wing was completed in 1847 when the palace chapel was consecrated. Along with the ducal family's private chambers, the west wing houses the poet's rooms furnished by Grand Duchess Maria Pavlovna between 1835 and 1847. These are memorial rooms in honour of Christoph Martin Wieland, Johann Gottfried Herder, Friedrich Schiller and Johann Wolfgang Goethe. The construction of the south wing in 1912 to 1914 under supervision of Grand Duke Wilhelm Ernst closed off the courtyard, which opened towards the park. The City Castle has been used as a museum since 1923. It is also the administrative headquarters of the Klassik Stiftung Weimar.
The City Castle also houses the Castle Museum with a large painting collection.