Trollhattan is a city and the seat of Trollhattan Municipality, Vastra Gotaland County, Sweden, with 46,457 inhabitants in 2010. It is located 75 km north of Sweden's second-largest city, Gothenburg. Trollhattan was founded on the river Gota alv, at the Trollhattan Falls. The site was first mentioned in literature from 1413. For centuries, Trollhattan was an obstacle for boats travelling the river, until a lock system was completed in the 19th century. It has since been updated several times, and the present locks were finished in 1916.