The Kaliningrad Region is the most western and smallest region in Russia. It is also the only enclave meaning its does not share a land border with the rest of Russia but with Lithuania and Poland. Historically this area was part of Prussia and the city of Königsberg, but it became part of Soviet Russia after the Second World War when East Prussia was ceded to the USSR. The German population left or were expelled and the Russians were moved in. Nevertheless the German influence, especially in terms of architecture, is still visible.
The administrative centre of the region is Kaliningrad (formerly Königsberg) which is famous for its connection with amber and even has a museum dedicated to it. It is even said that the original Amber Room is hidden somewhere in the Kaliningrad Region; the replacement though was certainly reconstructed using amber from Kaliningrad. Also located in the region is part of the Curion Spit which is a UNESCO World Heritage Site. If you plan to visit the Kaliningrad Region by land transport from mainland Russia, make sure you have a double or multiple entry visa.