A castro is a fortified settlement, usually pre-Roman, some from late Bronze Age and Iron Age, the oldest research associated with the Celtic culture. These are frequently found in the Northern Spain, particularly in Asturias, Galicia, Cantabria, Basque Country and the province of Ávila, with the Castro culture and on the plateau with Las Cogotas culture.
The word castro comes from the Latin castrum, which means "hill fort".
The castro is a fortified village that began to be inhabited from the 6th century BC, lacking streets of right angles and full of construction almost always circular. The oldest houses were mostly of straw-mud and the latest masonry. The roof was made of branches and mud and after long poles. Basically, they were unique rooms. These are located in naturally protected areas (heights, riots rivers, small peninsulas), close to water sources and arable land and on the border between these and higher areas of grazing.
The castros were protected by one or more pits, parapets and walls that bordered the inhabited recint, may have in its accesses a , which controlled the entryways to itself or another strategic location.
In times of conflict, the people who lived in open field moved to these strategically located buildings to ensure their safety. The buildings could also have other purposes such as control of territory, vigilance of crops, etc.
Its situation on the territory compared to other castros suggests that there was a definite strategy when choosing its location, allowing the communication by signals between them as a defensive network.
The maximum flowering time was between the 4th and 2nd centuries BC and show greater business contact with the outside of the south than the north, and the coastal than the inland. Some historians argue that in the first mid-1st century BC there was a multiplication of castros (either for population growth or for other reasons). At the end of the century, coinciding with the final phase of the Roman conquest, some with signs of destruction of the walls and in some cases immediate reoccupation.