Local dishes reflect a secular tradition marked by the seasons and by the life of a rural and mountain-dwelling society. Preparations are simple and involve local and regional produce: milk and dairy products (cream, butter and cheese), river and lake fish, cured meats, cereals (wheat, millet and corn) and potatoes. Cheese and, from the 19th century chocolate, are regarded as typical Swiss food products. Swiss cuisine is often defined by various key dishes such as fondue and rösti. These are regional dishes which are now popular across the country. The development of transport in the 19th century led to the spread of international influence but the identity of Swiss cuisine was built around potatoes in particular, with more dishes based on potatoes than in any other region of Europe.