A fire at a landfill site in Mont Cuet, Guernsey has been smouldering for three years.
(But the world's longest burning fire, known as the Devil's oven, is in New Straitsville, Ohio. It started burning back in 1884, when some unhappy miners pushed a burning coal car, filled with timber, down the mine shaft. So basically, the one on Guernsey is rubbish.)