This fountain is called Appearing Rooms and first popped up at the South Bank Centre in London in 2007 (this photo is from August 2018). The “walls” jet up and fall back with no apparent rhythm. If you’re brave (or willing to be soaked) you can make a dash for it. The people in this photo look content to stay in one place! On a hot day and with a change of clothes, it looks like great fun.