Kostrzyn nad Odrą (German: Küstrin) is a town in Lubuskie voivodeship, Poland, near the mouth of the rivers Warta and Odra. The German municipality Küstrin-Kietz on the Odra's west bank used to be the westernmost district of the former fortress town, but was split off when the German-Polish border was redrawn after 1945, putting Kostrzyn on the Polish side.

The old Kosterin was a settlement of the Slavic Pomeranians, which became on and off tributaries to Poland in the 10th century. About 300 years later, it was transferred to the Knights Templar, who were allowed to establish a market under German law. Around 1261, Küstrin and the formerly Polish county of Lebus became part of the Mark Brandenburg, which called this area Neumark.

From 1535 until 1571, Küstrin was the residence of some minor royal members of Brandenburg's Hohenzollern dynasty. During this time, the town was transformed into a fortress and a castle built. Further extensions in the 17th century made it one of the most fortified towns in Germany.

After receiving a railway connection in the 19th century, industry followed swiftly and settled nearby. Most military installations were removed after World War I, but it quickly became a military town again during Nazi times. During January/February 1945, in the final stages of World War II, the town was almost entirely destroyed, with roughly 10 % of the old town left intact.

Like its fellow border towns Frankfurt an der Oder or Görlitz, the part east of the Odra river was awarded to Poland after World War II concluded, leaving only the small district of Kietz on German territory. The German population was expelled and the old town's debris taken and transported to Warsaw, where it was used for the reconstruction of the capital. The modern Kostrzyn nad Odrą was built further inland and thus has little in common with the former river fortress.

Nowadays, Kostrzyn is little more than a somewhat drab border town – it attracts some (regional) tourists though, mostly Germans looking for cheaper shopping and people who want to visit the Ujście Warty National Park.

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Map of Kostrzyn nad Odrą

• 52.5810514.633581 Kostrzyn Fortress Museum (Muzeum Twierdzy Kostrzyn), Graniczna 1, ☏ +48 95 752 23 60, biuro@muzeum.kostrzyn.pl. 

• 52.579114.63592 Remnants of Kostrzyn's old town (Stary Kostrzyn). What's left of the original river fortress (pretty much nothing but a few cobble stones) can be walked through within 10 - 15 minutes. The gates on either end and part of the bastions have been renovated. In summer, having a lunch break on top of the Bastion Brandenburgia can be enjoyable, with views of the Odra. The inside (entrance ticket required) can be visited between April and October. Free. 

• 52.576314.62633 Former artillery barracks (Ehemalige Artilleriekaserne), Detlefsenstraße. Right before/after the border bridge, there are old fenced-off barrack buildings on the left and right side of Detlefsenstraße, which can make for an eerie scene on a gloomy autumn/winter day – the road sees little use. Built by the Nazis, the Russians took over and used the facilities after 1945, and left them to rot in the early 90's after Germany's reunification. 

• 52.5792214.642221 Polish market (Kostrzyn bazar). A typical border market mainly aimed at Germans who come to buy cheap(er) groceries, cigarettes, alcohol and clothing. Free parking. 

• 52.5867714.650122 Galeria Rondo. Small shopping centre containing a supermarkt, pharmacy and drugstore among other shops.