| The Street Numbering in Florence, Italy
According to a rule which applies in almost all of Europe, street numbers usually start from the principle geographical feature of the city, in this case, the river. If the street or square is parallel to the river Arno, the numbering of the buildings starts towards the source and increases in the direction of the outlet; if perpendicular, numbering starts from the river bank and increases away from it. Even numbers are on the right side and uneven on the left.
A double sequence of street numbering exists in Florence. Shops and businesses are identified by the letter 'r' after the number. This signifies 'red'. Private residences are numbered in black. Thus a street may have two number 18's, at times at considerable distance one from the other; 18r (as in the addresses given here) is a shop or business, while 18 is a private house. This is a practice that has been abandoned for new constructions, but the old roads still maintain it.