A Lid?

After digging deeper down, he witnessed that the object he had struck earlier was actually a metal lid! Now the mystery had intensified even more for John. He had to dig very deep all around in order uncover the extremely heavy metal lid. But, what was this lid actually covering? John had a similar question in the mind of which he was going to receive the most peculiar response very soon. It took some serious effort on the part of John in order to remove the extremely heavy metallic lid. Hours of toiling in the sun proved fruitful for him as he was now able to get a good look at what the lid had been hiding for years deep in his backyard. So what did he found out finally?

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