The town of Guernica, the "holy city of the Basques", lies in the valley of the Río Mundaca (also known as the Río de Guernica). In a square in the town, the Gernikazarra, under an ancient oak-tree, the Council of Elders (Batzarra) of Vizcaya (Basque Bizkaia) met every two years from the early Middle Ages
to discuss matters of common concern and transact business. The feudal lords of the region were required to appear before this assembly to guarantee the rights and privileges (fueros) of the Basques. The town of Guernica grew up around the Gernikazarra. The name of Guernica is now forever associated with the first mass air attack on an inhabited town. On April 16th 1937 several waves of bombers of the German "Condor Legion", which supported Franco in the Civil War, appeared over the town and within two hours had reduced it to rubble and ashes and killed 1645 of the inhabitants. Guernica was deliberately used by the Luftwaffe as a test-bed for the technique of area bombing. The massacre inspired Picasso's famous and controversial painting, "Guernica", which during the Franco period was hung in the Museum of Modern Art in New York and is now in the new Museo Nacional Centro de Arte Reina Sofía.