A very interesting and unusual card from Wroclaw.....
The card shows one of the medieval buildings on the Cathedral Island, which is one of the 12 islands in Wroclaw. (it feels odd to have the word 'island' related to a town :))
On the very site of Ostrow Tumski, sometime in the 9th Century, the first permanent settlers of Wroclaw, the Slavic Slezan tribe, built their stronghold. In those days Ostrow Tumski was an island, and a perfect place to built the heart of a settlement, with the protection of the river Odra running around it.
However, as far as its importance as the religious centre of Wroclaw is concerned, the date 1000AD is the key one. It was then, on the turn of the first millennium, that King Boleslaw the Brave earned the favour of Holy Roman Emperor Otto III and was able to establish a bishopric in Wroclaw. He chose to build a cathedral on this very promontory and the name Ostrow Tumski was born (literally 'Cathedral Island' in Old Polish). Ever since that day Cathedral Island has never ceased being the centre of religious life in Wroclaw - although it stopped being an island back in 1810, when a northern arm of the Odra was filled in.
History can be really interesting sometimes :)