We probably have multiple threads on illusions throughout the forum and over time we can try to reposition them here, because this is a topic that is discussed extensively in Lucretius Book 4, and it's interesting to talk about. It needs to be clear and emphatically understood that it is core Epicurean doctrine that error lies in opinion, rather than the senses, and that the senses report "truthfully" in the sense of "honestly" and that those who reject the senses are talking nonsense -- or "upside down" as Lucretius says.
This thought was spurred on by seeing this photo below cross my feed this morning. I'm not particularly pleased with the thought that is no doubt behind it, but I have to admit that this is an interesting illusion! And no, it's not anything of questionable underaged nature! 
The point generally being - ultimately the way to correct inaccurate opinions is through repeated and more precise use of the senses, not through rejecting the senses in favor of abstract logic or other non-sensual means.
I don't think I have seen one like this before -- interesting to think about how this was created.
I have a feeling this category could be very popular, so I encourage others to post similar illusions and discussions. Feel free to start new threads on each significant example.
