Winterthur is a city in the canton of Zürich in northern Switzerland. With over 120,000 residents, it is the country's sixth-largest city by populati…Winterthur is a city in the canton of Zürich in northern Switzerland. With over 120,000 residents, it is the country's sixth-largest city by population, as well as its ninth-largest agglomeration with about 140,000 inhabitants. Located about 20 kilometres northeast of Zürich, Winterthur is a service and high-tech industrial satellite city within Greater Zürich.