The place is called "Guernica". Guernica is a small town in the Basque country, not too far from Bilbao and Durango, where in the middle ages the parliament of the Basque chiefs was meeting and the national treasure of the Basques, the tree of Guernica, an ancient oak, under which the Basque chiefs would swear to support the Spanish king and the Spanish king would swear to preserve the internal autonomy of the Basque country.
At the time of the bomb raid, the Basque army was being forced westwards along a road, which lead over a narrow bridge over a river on the eastern edge of Guernica. The Fascist army wanted to cut off the way of restreat of this army to prevent them from regrouping in new positions. For this a fleet of Junker Ju-52 3m bombers (converted passenger planes) was sent to destroy the bridge and the adjacent buildings.
The planes, belonging to the German unit Legion Condor (sent as "volunteers" by Hitler) came in from the north over the Bay of Biscay and flew down the estuary of the river, heading south, at an altitude of about 2000 meters (appr. 7000 ft). Bomb aiming gear was rather primitive, consisting of a big bucket, which was lowered from the aircraft in the air, hanging between the main landing gear, with an bomb aimer in it using a simple bomb sight (not to compare wirh e.g. the gyro stabilised, autopilot connected Norden bomb sights of late WW2). The observer in the bucket would give instructions to the pilot using an electrical buzzer (one short buzz left, two short buzzes right, continous buzz straight ahead). The first planes missed the bridge (as did all others) and hit the adjacent buildings, raising a huge cloud of smoke and dust, which also prevented to following planes to see the target and caused them to drop their loads right into the cloud.
I don't know if there was any AAA around, but if yes, this might also have lead to a situation called a creep back were each pilot drops his load as early as possible to make his bomb run as short as possible to escape the dangerous zone of AA
As a result, while the intended target (as told to the bomber crews), the bridge, was not being hit, the built up area to the west of the bridge was completely destroyed.
One thing that puzzles me though is that the bomb loads consisted not just of HE
bombs, as required for the destruction of a target like the bridge, but also loads of incendaries. While the target was picked by midlevel tactical officers, the composition of the bomb loads came directly from the strategical top headquarters.
While the German officers were probably ignorant of the special significance of Guernica to the Basque people the Spanish fascist officers certainly knew about it.
BTW, both the house of parliament and the tree survived the war.
I was there in 1987 and saw both.