Poznań Fortress Days (14th)

For one weekend a year Poznań opens its fortress ring: the fourteenth Dni Twierdzy give access to twenty to thirty fortifications spanning a thousand years of military history, from the medieval walls of Ostrów Tumski through the massive Prussian fort ring of the nineteenth century to WW2 air-raid shelters and a Cold War command bunker. Guided tours - some by torchlight - run through forts, casemates and underground passages normally closed to the public, alongside re-enactment groups from several eras, military-vehicle rides, historical walks and a city-wide game for families. Coordinated by the city itself, it is Poland's largest fortification-heritage event.

Sites are spread across the whole city; the anchor is the Cytadela park (former Fort Winiary), which also houses the Armaments Museum, with the heaviest concentration of events along the nineteenth-century fort ring. Entry to most sites is free; some accept voluntary donations towards restoration. Printed programmes with a site map are available before the event, including at the Centrum Informacji Kulturalnej, and in recent editions a special heritage bus line has linked the forts (tickets sold on board). Bring sturdy shoes, a warm layer and a torch - the casemates stay cool even in high summer.