Sestao is a town and municipality of 27,296 inhabitants located in the province of Biscay, in the autonomous community of Basque Country…Sestao is a town and municipality of 27,296 inhabitants located in the province of Biscay, in the autonomous community of Basque Country, northern Spain. It is in the left bank of the Estuary of Bilbao and part of Bilbao's metropolitan area.