The Cañadas Reales are the network of transhumance paths covering 125,000 km of Spain , estimated to be 1% of Spain's surface area. Their immediate origin lies in the medieval transhumance system of paths, principally formed by the Mesta, along which livestock was permitted to travel and graze (cañadas, cuerdas, cordeles...). Each type of path stipulated the width permitted.

• cordal: cañada measuring 45 varas around 40 metres
• encañada : drover's road as it passes through a gorge
• vereda
• carrerada (Cat.); cañada
• valgada (Gal.); cañada

The cañadas (drover’s roads or traditional rights-of-ways for sheep) are, in theory at least, legally protected from occupation and barring, though this law has been much flaunted in recent decades.
Some of Madrid’s streets are still part of the cañada system, including La Castellana, and there are groups that organize sheep drives across the modern city as a reminder of the old practice, and in defence of the cañadas, as can be seen in this TVE video (30 Minutes):

Some authors suggest that some of the oldest cañadas are much more ancient, and go back to Neolithic times, and they themselves followed nothing less than the routes of migratory animals (deer, wild ox, etc) as they searched for winter and summer pasture, as in much of Africa today. The theory goes that humans first followed wild animals to hunt and then later continued with their tame beasts. It is a sobering thought to imagine that La Castellana, Madrid’s main thoroughfare, may have been formed by the ancient hooves of aurochs.

The Mesta was one of the biggest causes of deforestation as hundreds of thousands of sheep would traipse across the Peninsula every year, grazing and being fed with additional fodder.

The most important drover’s paths were the Cañadas Reales, each with many tributary paths:

• Cañada de la Vizana o de la Plata (500 Km).
• Cañada Leonesa Occidental (700 Km).
• Cañada Leonesa Oriental (700 Km).
• Cañada Segoviana (500 Km).
• Cañada Soriana Occidental (500 Km).
• Cañada Soriana Oriental (800 Km).
• Cañada Riojana o Galiana (400 Km).
• Cañada Conquense (350 Km).
• Cañada del Reino de Valencia (250 Km).

External links:

• The new cattle drovers. A conversation with Jesus Garzón". Excellent article in English from Wild-Spain
• Caminos de la transhumancia (source of the above video)
• Las cañadas (excellent Spanish review)