The Vilsandi lighthouse was built in 1809 on Vilsandi, an island off the western coast of Estonia biggest island, Saaremaa. Flashing lights with a rotating screen brought into motion by a clock mechanism and weights were taken into use in 1817. In 1860, a lighting system with Fresnel's dioptric glass prisms was installed. The Vilsandi lighthouse is situated at 58° 22' N and 21° 48' E.