Leave a pit for geomantic omen

First of all, it's best to stay away from the window, whether it's yours or your neighbor's. If it belongs to a neighbor, you are likely to have a conflict with your neighbor. . . Secondly, as you said, this is the only time in your life, so you'd better choose a good position before doing it ... Thirdly, as long as there are no negative substances in lime and sand, it won't interfere with Feng Shui. This is not a yin point, so there is no need to be so particular.