That reflects the future (today) where nothing is the way we believe. You have to look closely to notice, which most people do not.

This is The Arnolfini Portrait by Jan van Eyck, created in 1434. This painting features a couple, believed to be Giovanni di Nicolao di Arnolfini and his wife, standing in a room. One of the most intriguing aspects of the painting is the convex mirror on the back wall, which reflects two additional figures entering the room.

There is a reason we refer to these men of The Renaissance as Grand Masters. If you have yet to familiarize yourself with the panoply of the genius on offer, remedy and rectify that oversight.

The thread is pretty neat and explains it well - doesn't that mean the painting is not mysterious at all? What is there remaining that is mysterious?