The fortress was restored and used as residence by Paolo Guinigi in 1401; after his fall in 1429 this was again partially dismantled and later became the Palazzo Pubblico ("Public Palace").
After a period as the residence of Duchess Elisa Baciocchi, it was the seat of the Lucchese state government until the Unification of Italy in 1861, when it was acquired by the province of Lucca.
The palace is of large size and owes its current appearance to Bartolomeo Ammannati's restoration in 1578 (from the left side to the central portal).
On the left is another unfinished court, known as Cortile degli Svizzeri, referring to the corps of Swiss Guard in service of the Republic of Lucca, also designed by Ammannati and characterized by the use of rustication.
In the past the interior hall, accessed through a monumental stair by Nottolini, housed the National Gallery of Lucca, moved to Villa Guinigi in 1977.