El manantial "Los Barrancos" en Valdemorillo (Madrid) y sus aguas radiactivas.

The natural spring Los Barrancos de Valdemorillo was discovered at a scientific level in the first decade of the twen-tieth century, in the midst of boom of mineral waters and the spa culture, attracting great interest due to its highlevels of radioactivity. However, despite the owner’s efforts during decades to exploit it, it seems that the low waterlevel of the spring as well as the deep crisis experienced by the spa resorts, were enough reasons for this small spring,the most radioactive in Spain, to fade into oblivion since the middle of the twentieth century. This article gives anintroduction to the beginnings of natural spring spas with radioactive waters in Europe, and it documents the historyof the mentioned spring, from its discovery to the present day.