How Did Russia Keep Kaliningrad?

In 1945 the Potsdam Agreement was signed by the USSR (now Russia), Britain and the USA. It specifically gave Kaliningrad (known as the German Königsberg at the time) to Russia, without opposition. That's because Russia had already invaded and taken the area from Germany a few months earlier.

How does Russia control Kaliningrad?

All military and civilian land links between the region and the rest of Russia have to pass through members of NATO and the EU. Special travel arrangements for the territory's inhabitants have been made through the Facilitated Transit Document (FTD) and Facilitated Rail Transit Document (FRTD).

Why did Poland not get Kaliningrad?

Poland has made no claim to Kaliningrad, and is seen as being unlikely to do so, as it was a net beneficiary of the Potsdam Agreement, which also decided the status of Kaliningrad.