The Bastione dellâÂÂImpossibile is a 16th-century bastion in Trapani, Sicily, whose name derives from the marshy and unstable ground on which it was considered "impossible" to build. Following a long period of abandonment, the municipality of Trapani has outlined plans to reopen the monument for cultural use and limited public access.
Together with the Castello di Terra, the bastion formed part of the landward defensive wall that protected the eastern and south-eastern approaches to the city. This system complemented the northern seaward defences of the Mura di Tramontana, while the Castello della Colombaia controlled maritime access at the western tip of the peninsula. Together these works formed a continuous defensive circuit enclosing the historic city.
In the early 1520s Trapani's landward defences were strengthened as part of a wider response by the Spanish crown to the growing threat of Ottoman and North African piracy, and in 1523 the viceroy Ettore Pignatelli appointed the Paduan engineer Pietro Antonio Tomasello to redesign the city's medieval walls according to the new bastioned principles.
The bastion was constructed at the southern end of Trapani's landward defensive wall in an area of marshy ground historically associated with salt-pan activity. Much of the earth and stone required for the works came from the large-scale excavation of a new landward moat undertaken during the same fortification programme.
Much of the adjoining defensive wall was demolished during 19th-century urban redevelopment, and the remains of the landward fortifications were subsequently incorporated into later buildings along Via Spalti. Despite these alterations, traces of the 16th-century perimeter remained visible in early 20th-century cartography, and the surviving masonry of the bastion continues to mark the line of the former landward defences.
After a period of abandonment, the Bastione dellâÂÂImpossibile returned to municipal availability in 2021 through an agreement between the Comune di Trapani and the Agenzia del Demanio, the Italian state property agency. The municipality subsequently carried out cleaning and clearance works in 2022 and announced plans to stabilise and refurbish the structure for cultural uses, including reopening a panoramic terrace and adapting the interior for artistic and community activities.
As of 2025 the bastion remains closed to the public. Local reports indicate ongoing discussions regarding its management, with the possibility of future concession through the Demanio as part of broader efforts to enhance Trapani's historic fortifications.