Have you spotted the large concrete blocks that feature concave divots cut out of them in the UK? Do you know their true purpose? It is okay if you do not since most people don’t know why these concrete mirrors were built. Allow us to explain why; about a hundred years ago, the British government constructed these concrete mirros as means of picking up the sounds of approaching airships thus helping it to figure out when the Germans were coming.
When you think of air raids against the UK, you are probably thinking about the Nazi attacks from World War II. However, that wasn’t the first time that the Nazis had air raided UK. The concrete mirrors were constructed for Germany’s zeppelin force of World War 1. You can learn how a zeppelin works here.
These blimps were loaded with bombs and crossed the North Seas and the Baltic to attack the United Kingdom. The purpose of these attacks was to lower the morale and to drive Great Britain out of the war. The zeppelins being used were the German P-class airships that could carry three tons of bombs. They were powered by four Maybach 3M C-X 6-cylinder inline piston engines. The airships could achieve a speed of 57mph.
Germany began the bombing in the UK in 1915. This is a time before the radar was invented. British engineers were tasked with a way of finding out about the German attacks in advance. The result came in the shape of the concrete block with a concave surface. These structures were built facing the direction of the approaching German zeppelin force. The concave surface would pick up the buzz of the airship engines before the human ear thus would grant ample time for air and civil defenses to be ready for the attack.
After 100 years of construction, these amazing devices are still in existence. Although their purpose has become obsolete ever since the advent of radar. The concrete structures vary in size and shape. The BBC has a gallery of these unique and creative devices!