In Salzburg, Austria we stopped by the Salzburg Cathedral. The cathedral has a courtyard around it with an entrance that includes the Immaculate Mary column in front of the cathedral (top picture). As you enter the courtyard moving toward  Mary (bottom 2 pictures) there is an optical illusion called the “crowning of Mary”. In the facade of the cathedral above the entrance there are 2 angels holding a gold crown, and as you approach the angels and the crown they are holding decend until the crown appears to be on her head.