Ostrów Tumski — Cathedral Island — is a small island in the Warta River where the Polish state began. This is where Duke Mieszko I accepted Christian baptism in 966, an event considered the founding moment of Poland as a political entity. The cathedral, the bishop's palace, and a handful of historic buildings occupy the island, which is quiet, tree-lined, and largely free of traffic.
The contrast with the busy commercial city centre is striking. The island feels like a separate world: old cobblestones, the smell of river mud, ducks on the water, and the twin towers of the cathedral visible above the roofline. It is best visited on a walk that continues across the bridge to the main city — the 20-minute stroll through the old cathedral district and back across the river gives a good sense of how the city grew outward from this original nucleus.