Ziemia (Polish pronunciation: [ˈʑɛmja], Land) is a historical unit of administration in Poland. In the Polish language, the term is not capitalized (ziemia chełmińska, Chelmno Land; not Ziemia Chełmińska). All ziemias are named after main urban centers (or gords) of a given area: ziemia krakowska (after Krakow), or ziemia lubelska (after Lublin). In some cases, the suffix "-szczyzna" is added to the name of a ziemia: ziemia lubelska is also called Lubelszczyzna, while ziemia opolska (named after Opole) - Opolszczyzna.
More information on the Wikipedia page , which has a list of ziemias in the Polish-Lithuanian Commonwealth.