Road Numbers
In the Plaza del Sol, in Madrid, capital of Spain more frequently than not since 1561, there is a plaque set in the pavement marked as Kilometre Zero. If Google Maps tells you that it's 395 km to Madrid, that's the point it's measuring to. As a local aside there's a similar point in Murcia in the street called Platería. There are a series of arterial roads that radiate from Madrid. The arterial roads have numbers prefaced by the letter N for Nacional/National. The six radial roads were given Roman numeral names, NI, NII, etc. As examples, the NIII goes to Valencia from Madrid. The NIV goes from Madrid to Seville and on to Cádiz. The effect is that Spain is divided up, cake-like, into slices or segments. Any main road, any national road, in the slice between the NIII and NIV, in a clockwise direction, will have a number that starts with N3. The NV goes to Badajoz from Madrid. Any road clockwise of the NIV but before the NV will have a name in the style of N420. Lots of u...