
The day of Sant Joan is very ancient festival which celebrates the arrival of the summer solstice in the northern hemisphere whose principal rite is a fire.
The purpose of this rite was "give more power to the sun, which from that time, was becoming "weaker"", the days are getting shorter until the winter solstice.
Symbolically, the fire also has a function "cleansing" in people watching him. Previously also loosed the dogs to drive the evil spirits.
In Barcelona, you can enjoy of this party in some corner in the street, where the people prepare a fire with all the old thing in the house. Or you can go to the beach, to wait for the dawn while enjoing the fire, the music, the drinks and the friends!