Igloo, or snowhouse, was a winter dwelling utilized by Inuit across the Arctic. Some Inuit spent most of the winter in semisubterranean houses made of driftwood and whalebone and only used the igloo when travelling. Others relied on igloos for housing through the entire winter. The dome-shaped igloo was built spirally from within. The structure derived its strength from the key block, inserted at the apex of the roof. A series of these domes were constructed, connected by passageways, to house 15-20 people. Furniture consisted of cooking pots, oil lamps and low platforms. Temperatures inside the igloo were just below freezing or warmer.