Sant Joan is the night Spain stays up to greet midsummer, and El Perelló keeps it gloriously local. The whole town spills onto Plaça de l'U d'Octubre for dinner in the open air, long tables filling up as the light fades. Then the bonfire goes up in the middle of the square, there's a marked-off corner for setting off firecrackers, and DJ Cris works the pergola with a steady run of 70s and 80s tunes until around 2am.
It's a neighbourhood do rather than a tourist spectacle, which is exactly the appeal. If you fancy sitting down to eat, you'll need to book a table and chairs through the Tourism Office beforehand, though you're just as welcome to wander in, stand near the flames and dance. Bring a jumper for the small hours and join the party.