In the Soviet Union and the mentioned post-Soviet republics, oblasts are one step below the national level and further subdivided into districts called raiony or rayony (Russian: райо́ны; Ukrainian: райони). The word is often translated as "province" or "region".
In Bulgaria, the top-level subdivision is into regions, with further division into oblasts.
Oblasts are purely administrative units without any significant history: all of them have been formed in the middle of the 20th century.
The administrative borders of several oblasts have sometimes been changed in order to reshuffle the local Communist Party organization, secure "the right" local administration for an industrial company, limit an ethnic activism etc. Such decisions were a Soviet version of the gerrymandering method of affecting a vote.
Kaliningrad Oblast (Russian: Калинингра́дская о́бласть), informally called Yantarny kray (Янта́рный Край, meaning Amber region) is a federal subject of Russia (an oblast) on the Baltic coast, with no land connection to the rest of Russia; it is a non-contiguous exclave of Russia surrounded by Lithuania, Poland and the Baltic Sea.
Its largest city is Kaliningrad (formerly known as Königsberg), which has historical significance as both a major city of Prussia and the capital of the former German province East Prussia, of which the region remains the core remnant.
The Kaliningrad Oblast is the fourth most densely populated oblast in the Russian Federation (62.5 persons per sq.km).