Szlachta:

The tribes were ruled by clans (ród) consisting of people related by blood or marriage and theoretically descending from a common ancestor, giving the ród/clan a highly developed sense of solidarity. (See gens.) The starosta (or starszyna) had judicial and military power over the ród/clan, although this power was often exercised with an assembly of elders. Strongholds called grόd were built where the religious cult was powerful, where trials were conducted, and where clans gathered in the face of danger. The opole was the territory occupied by a single tribe. (Manteuffel 1982, p. 44)

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What was the territory occupied by a single tribe?
opole