All the streets of the cities have different names and all the buildings are identified with different numbers. I was walking by the streets near Park Güell of Barcelona when I noticed this figure identifying the second door of a building: number 7,5! Have you ever seen this number over the door of a house? In Barcelona, you can see two doors in the same building and one is identified with a number and the other is identified with the same number followed by the word BIS. However, it’s the first time that I saw the fraction HALF!