At 3.30 AM on Saturday 25th April 1998 the south coast of Spain was host to what has been dubbed the worst environmental disaster in Europe.

A supporting wall of the reservoir containing the toxic wastes of the Aznalcollar mine burst, releasing 5 million cubic metres of toxic mud and acidic water onto the surrounding landscape. The toxic waste entered the Agrio River, a tributary of the Guadiamar River, which feeds the swamps of the Guadalquivir situated within Doñana National Park and the Natural Park of the Environment of Doñana.

The Natural Park is a wetland of international importance under the Ramsar Convention, as well as part of UNESCO's global network of Biosphere Reserves.