The image shows a sign on a subway platform in Madrid, Spain. The sign is rectangular in shape and has a black background with white text. On the top left corner, there is a drawing of a person smoking a cigarette. Below the drawing, it reads "Metro de Madrid" in Spanish. 

The sign also has a red circle with a line through it, indicating that smoking is not allowed in the area. The text on the sign reads "Artículo 31 Reglamento de Viajeros" which translates to "No smoking allowed" in English. The platform is empty, with no people visible in the image.