CassandraW1. There are some fascinating traditional festivals that take place around the globe every month but probably none more bloody (and few more colourful) than the Andean festival of Tinku. Each May, thousands of indigenous Bolivian indians ascend upon the isolated, mountainous city of Potosi looking to pick a fight. In a ritual dating back 600 years, local indians slug it out, toe-to-toe until blood is spilt. The spilt blood - an offering to the earth goddess Pachamama - should ensure a successful harvest for the coming season.