The castle of Piombino is the main defensive military work that remains in the city, located on the Hill Southeast jutting out into the sea. The castle was the landmark of the city on that side and opened a city gate.
The castle was originally built by the Pisans in the XIII century and was then called “Cassero pisano”, with its robust mole nearly cubical; it was enhanced by Leonardo da Vinci when he took charge of the reorganization of the city defences.
The Castle has been restored and was the subject of archaeological excavations between 1999 and 2001 by architect Piero Ostilio Rossi. Today it houses the Museum of the Castle and the city of Piombino, which traces the history of the building in the context of the events in the city. There are some 13th century objects found during excavations: on the ground floor a number of utensils like dishes, buckles, jugs, oil lamps, coins, plates of armor, arrowheads and lead bullets; on the second floor shows the history of Piombino in the resistance and in the 20th century.