Every year on the small Greek island of Chios (pop. about 51,000), two “rival” churches in the town of Vrodandos have a rocket war during Easter mass. The goal is to hit the opposing church’s bell tower with one of the 25,000 fireworks while the priest continues to say mass.
The rockets are made, illegally, by the town’s residents over the course of the year, though the police turn a blind eye to the process (presumably because it’s a longstanding tradition). The story behind the tradition is unclear, however it may be a link to the island’s days of fighting off pirates in which cannons were shot off at Easter. When the Ottomans removed the cannons in the late 19th century for fear of an uprising, residents started making rockets.*