A house made of ice is called an igloo. Igloos are traditionally used by the people of Canadas Central Arctic and the Qaanaaq area of Greenland, and are built of suitable snow. The word "igloo" is not restricted exclusively to snowhouses, but includes traditional tents, sod houses, homes constructed of driftwood, and modern buildings. The dome shape of an igloo helps to trap interior heat in the space, and snows insulating properties enable the inside of the igloo to remain relatively warm. Sometimes, a single block of clear freshwater ice is inserted to allow light into the igloo.