The urban layout in the center of the city is based on the focal point of a square or plaza, typical of Spanish-founded settlements, but the layout gradually becomes more modern in outlying neighborhoods. The types of roads are classified as ''Calles'' (streets), which run from west to east horizontally, with street numbers increasing towards the north, and also towards the south (with the suffix "Sur") from Calle 0 down south. ''Carreras'' (roads) run from north to south vertically, with numbering increasing from east to west. (with the suffix "Este" for roads east of Carrera 0). At the southeast of the city, the addresses are logically ''sur-este''. Other types of roads more common in newer parts of the city may be termed ''Eje'' (Axis), ''Diagonal'' or ''Transversal''.