It has stood upright for nearly 6000 years and is viewed as a nationally important archaeological site.
But Dane's Stone, an ancient rock that lies in Moulin, Perthshire, has come crashing down to earth after the surrounding ground was pounded by incessant rain.
Marianne Carruthers was sitting at home 50 yards away when she heard the 7ft landmark - thought to date back to the neolithic era or Bronze Age - smash into the muddy ground.
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She said: "I went to the window but couldn't see anything. It wasn't until half an hour later that I noticed something was amiss and the stone just didn't seem to be there anymore.
"I actually took off my spectacles and cleaned them because I thought I was seeing things. I couldn't believe it."
Luckily, the quartzite stone, which was once part of a stone circle before the other rocks were removed and buried underground, does not appear to be damaged.
A spokeswoman for Historic Scotland confirmed a team of experts had visited the scene and moves would be made to lift the stone back up.