Blida was hit by a powerful earthquake on 2 March 1825. The shock was strong enough to almost wipe out the entire city, with thousands of residents killed.
Northern Algeria sits in a collision zone between the African and Eurasian plates, and Blida lies on the southern edge of the Mitidja plain, an area shaped by active thrust faults. These same geological forces have produced other major earthquakes in the region.
The quake struck around 07:00. Its force was extreme, followed by several strong aftershocks over the next few days.
Blida was left in ruins, with only a few structures still standing. Algiers, about 50 km away, felt little impact aside from possible cracks in the Casbah. Witnesses reported the ground splitting open and wells and springs drying up shortly before the main shock.
The death toll reached at least 6,000, likely more. Many victims were caught inside collapsing mosques during morning prayers.