Unsurprisingly, given the climate, the oven was at the heart of any Russian peasant's home. The traditional peasant cottage (izba) would be made out of logs, with a huge brick oven in the centre, often with two hearths: one for cooking and one for warming the house. Russian ovens are extremely efficient wood burners that use a complex chimney system to heat the bricks, ensuring that they have an extremely long cooling down period. A well-made oven would require fuel two or three times a day at the most. The structures are so large that during the Great Patriotic War (the Second World War) men used to hide from Nazi soldiers within their ovens. In the winter, people would sleep on shelves on top of the oven to keep warm.