The citadel was the fortified heart of Baturyn, the city that served as the capital of Ukraine's Cossack hetmans in the 17th and 18th centuries. First raised in the early 1600s as a Polish outpost, it became from 1669 to 1708 the official residence of a line of hetmans - Demian Mnohohrishny, Ivan Samoilovych, and most famously Ivan Mazepa. From behind its walls and towers the leaders of the Cossack Hetmanate governed the autonomous republic of Left-Bank Ukraine. It was a seat of real power, a working capital with a garrison and cannon, until the autumn of 1708, when a single fateful decision brought the full weight of an empire down upon it.

The chain of events reached back to 1700, when the Great Northern War set a Muscovite-led coalition against the Swedish Empire, and the Cossacks were made to fight the tsar's war on every front, bleeding men and treasure. In the autumn of 1708 Hetman Ivan Mazepa made his choice: he allied with the Swedish king Charles XII. Tsar Peter I answered by ordering the capital destroyed. He sent Alexander Menshikov to take Baturyn, and at first the twenty-thousand-strong army could not storm the fortified city. Only after a secret way in was betrayed did the attackers overwhelm the defenders. Historians estimate that between thirteen and fifteen thousand people were killed - soldiers, yes, but mostly civilians, women and children among them. The victors looted what they could carry, then burned Baturyn and the villages around it to the ground.

The main fighting, archaeology has shown, raged inside the citadel and the fortress walls - and for almost three centuries, what happened there went deliberately unspoken. Only with Ukraine's independence did it become possible to speak and write openly about the tragedy. Excavations began in 1996, and in 2008, on the initiative of President Viktor Yushchenko, the citadel was rebuilt in situ - the only open-air archaeological park of its kind in Ukraine. Its towers and walls do not claim to be the originals; they offer a generalized image of the Baturyn castle as it stood in the early 18th century. At the centre rises an eleven-metre cross of dark granite, raised in 2004 to the thousands who died, bearing a bronze crucifix - a symbol, its makers said, of a Baturyn crucified and resurrected. Here the fortress remembers not a battle so much as the people it could not save.