Rewilding Europe are releasing vultures, lynx and wild horses in 850,000 hectares (2.1m acres) of land in the Iberian highlands east of Madrid.
The area is described as one of the least populated on the continent, with numbers more than halving in the last 70 years, making it a perfect space for nature regeneration.
A batch of black vultures have already been released in September, with 15 more to follow each year. Meanwhile, 11 semi-wild horses have already welcomed their first foal. Iberian lynx will see planned reintroduction to the area within the next year or two.