Grounding was an important aspect in the energy grid. Apparently certain grounding points in the Earth gave off more energy. This makes sense with our knowledge of fractals: a method of increasing energy output by means of symmetry.

There used to be a practice called Geomancy which to my knowledge is essentially the practice of mapping out energy zones in an area. Think about it this way:

The old world buildings, which harnessed energy, were purposefully symmetrical like a fractal.

The old world cities by extension were also shaped symmetrically or like fractals using the symmetrical buildings.

But what does this mean?

This means that if one knew the certain fractals of a certain old city, one would be able to "fill it back in" and discover where the destroyed buildings were once located in an area.

Let's expand further and assume the old world was very united. Take note of all the cities in a certain big area and the shape they create. If it is incomplete, you may be able to find long lost cities.