Sobrino de Botín (Calle de los Cuchilleros 17, 28005 Madrid, Spain), founded in 1725, is the oldest restaurant in the world in continuous operation.
The restaurant is mentioned in an Ernest Hemingway novel and the book Fortunata y Jacinta by Benito Pérez Galdós (published 1886-1887).
Apart from using the original recipes, the restaurant has also kept the flame burning in the oven continuously, never to be extinguished.
The restaurant and its speciality of cochinillo asado (roast suckling pig) are mentioned in the closing pages of Ernest Hemingway's novel The Sun Also Rises. Its other signature dish is sopa de ajo (an egg, poached in chicken broth, and laced with sherry and garlic): a favorite pick-me-up with Madrileño revellers.
According to en.wikipedia