The southern border town of Cieszyn (pronounced cheh-sheen) is one of Silesia's oldest settlements. According to legend, it was founded in 810 by three brothers -- Bolko, Leszko, and Cieszko -- to celebrate their reunion. More likely, the city dates from around 1200, first emerging as a defense post along the traditional border between the Polish and Bohemian kingdoms, and then later developing into a trading center. Cieszyn served as the capital of the independent Duchy of Cieszyn from the end of the 13th century to the middle of the 17th century, before falling under the domination of the Habsburg Empire. Today, it's interesting for two reasons. One is that it's a nicely preserved medieval market town, with the original street plan intact, a handsome square, and -- naturally -- an impressive castle. The second is more geopolitical. In more modern times, Cieszyn proved to be a thorn in the side of Polish-Czechoslovak -- later, Czech -- relations. The town's roots are Polish, but the competing dynastic claims through the ages muddied the waters. At the end of World War I, Cieszyn was split down the middle along the Olza River, with one side going to newly independent Poland and the other side, known as Ceský Téšín, to the newly founded Czechoslovak state. The darkest moment arguably came ahead of World War II, in 1939. Just as Hitler was grabbing Czechoslovakia's German-speaking border regions, Poland forcibly annexed the Czech side of Cieszyn. At the end of the war, the original borders were restored, but the memory soured bilateral relations for decades. Now, with both countries in the European Union, all seems forgiven, and Cieszyn/Ceský Téšín has been officially declared an EU "Euroregion." Indeed, you're free to walk at will from one bank of the Olza to the other, enjoying the oddity of a town that is literally half-Polish and half-Czech.