An arrow slot of a stone tower. Taken in Bratislava, Slovakia, September 2015, using the iPhone pano feature. By gently rocking the phone back and forth while panning, you can get pano to produce these undulations.

Here’s the same effect, this time with a carved relief of the Last Supper in St. Martin’s cathedral. The undulations of pano give the scene the liquid feel of an El Greco. This version seems to me to be more uneasy, more expressive than the original.