The Lady in the wall

The company where I worked before called me up. They said that they had some unusual phenomena in the new building they are constructing. A face of a lady appeared on the wall. I was curious so I went to investigate.

According to my brother, who is an engineer, this phenomenon usually happens in doing concretes. Images form through some water marks. But they would eventually disappear.

What's the weird part about this image, we tried to wet it with water, rub it with "papel de liha" but it's still there.

What this image is telling us?

For now, the investigation is still on going regarding this image.