Two rivers cross the region, the Wolbórka and the Luciąża, which with their tributaries flow into the Pilica River and belong to the catchment area of the Vistula River. The watershed of Poland's two main rivers, the Vistula and the Oder (Odra), runs along the meridional line three km west of Piotrków. Two small rivers, the Strawa and the Strawka flow through the city, and it is between their valleys that the first settlement of Piotrków was founded in the early Middle Ages. Recently two more rivers have been included within the boundary of the city area - the Wierzejka, which in the western part of the city forms a reservoir, and the Śrutowy Dołek to the south of Piotrków.