Strange Marked Rock Found on a Yambol Road

In the middle of nowhere on a Yambol road on the outskirts, a strange marked rock was found embedded in the tarmac. There is a mysterious inscription on the side as well. Who knows?

Strange Metal System in a Yambol Street

I fail to figure out what this strange metal system is on a street in Yambol. It is a permanent fixture going underground. I am guessing it might be something to do with water, but it remains a mystery. 

A Strange Front Door In Yambol

The reason I find this front door strange whilst passing it is the small holes that have been made on the panes in the upper half. Why? Ventilation first springs to mind but I'm sure there is another reason. Maybe I'll never know. The electric bill has been stuck on the door handle by the way.