Optical illusion

[Helen Jane]

so it has no relief after all?

[Marloes]

@helenhall sometimes you see it as hollow and sometimes it pops to convex. It's snow with relief.

[Helen Jane]

@stimuloog my eyes only see the hollow. I didn't clock it as snow either.

[Marloes]

@helenhall Turning the image can help ;) and it's just a bad snow pic. Far too blue...

[Daryl O'Hare]

Intriguing!