The Aznalcóllar mine disaster occurred on April 25, 1998, in Aznalcóllar, Spain, when a dam at the Los Frailes mine collapsed. This failure released approximately 5 million cubic meters of toxic sludge, containing heavy metals, into the surrounding environment, affecting nearby rivers and ecosystems. The spill contaminated the Guadiamar River and caused significant damage to local agriculture and wildlife. The disaster prompted widespread concern over environmental safety and led to legal actions against the mining company, Boliden, for negligence and inadequate safety measures. Cleanup efforts were initiated to restore the affected areas.