Long, long ago, Penny and I were mystified by a circle of dead grass that appeared in a local park.
We did figure eventually that the grass had been sprayed in order to prepare the spot for an indigenous planting.
And now the planting is flourishing.
It's a pity that they probably used a horrible, dangerous herbicide on the spot originally, but I guess we'll have to hope it hasn't remained in the ground. (But latest science seems to indicate it stays around longer than Monsanto would have us believe.)