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Huge concrete acoustic mirror used in WW1 to detect plane/zeppelin engines before radar. Many still remain down the coastline. Sunderland, NE, England. | /r/mildlyinteresting
Uploaded by Reddit Moments Oct 02, 2020 at 04:02PM EDT
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Origin Entry: Mildly Interesting
File type: jpg
Resolution: (640px x 454px)
File size: 46 KB
