Why is this symbol in the middle of nowhere?

What is this?
Why that is a nuclear symbol…

Mounted on a deeply embedded very heavy steel bar/beam….looks like someone still tried to run over it at one time though…

Forestry Department area. Svetochka and I just walking….

Looks like an old fallout shelter symbol…

Hmm…

WtR

A survivor of six heart attacks and a brain tumor, a grumpy bear of a man, whom has declared Russia as his new and wonderful home. His wife is a true Russian Sweet Pea of a girl and she puts up with this bear of a guy and keeps him in line. Thank God for my Sweet Pea and Russia.