Have you ever noticed those markings? You can see them in many blocks in Madrid, next to the names of the streets.
They are from the 18th century, the time of the General Planimetry of Madrid.
In order to have an efficient way to collect taxes the government numbered the blocks. Also around the block the doors were numbered and so the inspectors took information from every house.
The problem of that numbering system was that in the same street they had repeated numbers and for the everyday life they had to resort to other references.
(“Visita GL” means General Visit and “Manzana N” means Blook number).
