Ljósifoss, a waterfall in the river Sog by Efri–Brú. Two power stations in the Sog are associated with it, Ljósifoss, harnessed in 1935–37 and 1934–44, total power 15 MW and Írafoss–Kistufoss, harnessed in 1950–53, power 48 MW. A community which has grown up around the stations and has its own school takes its name from the falls.