Street numbers
Florence has a confusing dual address system. Each street has a double set of numbers: a red number indicates a shop, restaurant or business, while a blue or black number refers to a hotel or domestic residence. When writing to a business, insert an “r” after the number to distinguish it from a residential address. Each set of numbers has its own sequence, so business premises at, say No. 10r may well be next to a residential address at No. 23. [Eyewitness travel: Florence & Tuscany (Dorling Kindersley, 2007) p. 298.]