The river Oder/Odra at Wrocław

"City of Bridges"
Wrocław is a city on the river Oder - Odra in Polish - located on twelve islands, and has well over a hundred bridges.  The precise number seems to depend on how you define a "bridge", but there is mention of there having been over 300 of them before World War II.

Oder-Neisse line
The Oder flows north-westwards from Wrocław.  The stretch from (German) Frankfurt an der Oder to (Polish) Stettin, where it meets the Baltic Sea, has since 1945 demarcated the boundary between Poland and Germany.

Cathedral Bridge
Most Tumski  leads to the cathedral of St John the Baptist on (you have probably already guessed) Cathedral Island.  Building work in brick was started in 1244 and continued for five centuries;  the cathedral's towers and part of its facade can be seen in the background.