Lieto is a city and municipality of Finland. It is located in the province of Western Finland and is part of the Southwest Finland region. The mu…Lieto is a city and municipality of Finland. It is located in the province of Western Finland and is part of the Southwest Finland region. The municipality has a population of 20,620 and covers an area of 302.56 square kilometres of which 1.66 km² is water. The population density is 68.61 inhabitants per square kilometre.