Guinness is a popular dry stout that originated in Arthur Guinness' brewery at St. James's Gate in Dublin, Ireland. The beer is based on the porter style that originated in London in the early 18th century. It is one of the most successful beer brands in the world, being exported worldwide. The distinctive feature in the flavour is the roasted barley which remains unfermented. The thick creamy head is the result of the beer being mixed with nitrogen when being served.