The tribal states built many gords – fortified structures with earthen and wooden walls and embankments – from the 7th century onward. Some of these were developed and inhabited; others featured a large empty space and may have served primarily as refuges in times of trouble. The Polans settled the plains around Giecz, Poznań and Gniezno that would become the early center of Poland and lent their name to the country. They went through a period of accelerated building of gord-type fortified settlements and of territorial expansion, beginning in the first half of the 10th century, and the Polish state developed from their tribal polities in the second half of the 10th century.