It´s a french word that means "deceive the eye", as it´s possible to see at the picture above, what it seems a dome is just a plain ceiling of the Rabat (or Victoria) Cathedral in the island of Gozo in Malta. The optical ilusion seems another thing that it isn´t. It´s a realistic way of pictures (in this case a fresco painting). And this one of Gozo, althought is not the unique one, is one of the most popular.

Picture taken in Gozo Cathedral in Malta