For years, people in the British countryside have been flabbergasted by the sight of certain strange stone objects. The enormous structures seemingly served a purpose, but their origin remains a mystery to the average citizen… until now.

While they may have seemed similar to the famous Stonehenge monuments, these bizarre concrete creations were something far more modern. The work of Dr. William Sansome Tucker, these oddities were actually built in the early 20th century and used as “acoustic mirrors.”

The reason for these baffling objects’ existence, however, only becomes more fascinating from there…

The world’s first truly efficient radar system was invented by Scottish physicist Sir Robert Watson-Watt in 1935. It was capable of detecting enemy aircrafts from up to 100 miles away using pulsed radio waves. Before that watershed invention, however, the British military looked to make use of something far more bizarre… and you can find them littering the English countryside to this day.