On the Royal Mile, Edinburgh, lies the Heart of Midlothian.From Wikipedia:-

Visitors to Edinburgh will often notice people spitting on the Heart. A tolbooth (prison) stood on the site, where executions used to take place. The heart marks its doorway: the point of public execution. Some people spit on the Heart. Although it now said to be done for good luck, it was originally done as a sign of disdain for the former prison. The spot lay directly outside the prison entrance, so the custom may have been begun by debtors on their release.