To the east of the Old Town, over the Warta River, is the island of Ostrów Tumski (Cathedral Island). You’re walking through deep history here, the place where Poznań was founded, and with it the Polish state. The original 9th-century settlement was gradually transformed into an oval stronghold surrounded by wood-and-earth ramparts, with an early stone palace. Mieszko I added a cathedral and further fortifications, and by the end of the 10th century Poznań was the most powerful stronghold in the country.
In the 13th century, when Poznań had spread beyond the island and the newly designed town was laid out, Ostrów Tumski lost its trade and administrative importance, but remained the residence of the Church authorities.
This river island is dominated by the monumental, double-towered Poznań Cathedral, originally built in 968. The Byzantine-style Golden Chapel (1841) and the mausoleums of Mieszko I and Bolesław Chrobry (known as Bolesław the Brave) are behind the high altar. Opposite the cathedral is the 15th-century Gothic Church of the Blessed Virgin Mary. The island is 1km east of the Old Town.
The island has a rather unique village atmosphere and rewards an aimless stroll. At ul Śródka 3 (in the Śródka district as you approach the island from the east) you'll find an enormous trompe-l'œil mural depicting Śródka in the 1920s.