Porto's Festa de São João is one of Europe's liveliest street festivals, yet it is relatively unknown outside of the country. Nearly every Portuguese town and village adopts one of the santos populares, the popular saints of António (Anthony), João (John) or Pedro (Peter), whose days all fall in June, probably a Christian adaptation of pagan summer solstice celebrations. There remains a strong religious element to the festivals, but in an increasingly secular country, the church services and religious processions are often overshadowed by the riotous party element.

As the evening progresses, there remains a healthy mix of all ages, from elderly couples to young children, a combination that neatly tempers the behavior of the chanting male youths in replica Porto football shirts.

Then the first hammers appear. No one seems to know the origins of hitting people on the head with a leek, but now the softer plastic hammers have become the preferred mode of attack. Luckily, even the most macho tripeiros hit with surprising restraint, especially as people of the opposite sex are usually the targets.

The tide of whistle-blowing locals flows into the precipitous labyrinth of narrow streets tumbling downhill from São Bento station to the riverfront Cais da Ribeira. This is where Porto's best bars and restaurants are found, but during the festival they are outnumbered by hastily erected barbecues, stalls selling Superbock beer and makeshift stages blaring out live music varying from pop and rock to traditional fado. The smell of grilling peppers and sardines wafts through the warm June air.