Walk in circles for 10 minutes in front of Porto City Hall (Câmara Municipal do Porto)

Go to the square in front of Porto City Hall (Câmara Municipal do Porto, Praça do General Humberto Delgado, top of Avenida dos Aliados). Walk slowly in circles on the square, directly in front of the City Hall building, for 10 continuous minutes. Be respectful of other people and do not block traffic or entrances. Record a video: at the start show the City Hall building behind you, keep recording (or record at start, middle and end), and show a phone clock or timestamp at the start and at the end so the 10 minutes are verifiable.