A great number of surviving towns in Teruel province have only a residual population, reviving somewhat during the summer when a few city-dwellers spend their holidays there. Other causes of the strong emigration have been the low productivity of traditional agricultural practices, like sheep and goat farming, the closing of mines, like the large Sierra Menera mine near Ojos Negros, as well as the lifestyle changes that swept over rural Spain during the second half of the 20th century.