"Weird excavations at the construction site of a highway. Symmetrical, look like sculpted out of the ground, 2-4 meters across, up to 1m deep. Only thing that comes to mind are archeological excavations? Or some kind of ground cross section analysis?"
A: "Most definitely archaeological excavations prior to the building of the highway. Most European countries have heritage laws that impose preventive archaeological surveys before major public projects. The shape of the “holes” is the result of a systematic search for archaeological artifacts at different stratigraphic levels."
I have one for each of my extension cords.
Pur coals inside and then place under covers.