Next Saturday is the annual Reykjavík Cultural Night.
Various evetns are both planned(and also not planned) in downtown Reykjavík and sourrounding areas.. High art, music, dancing, reading, theatrics and more is on during the day and until 11 p.m. where a fireworks show signals the end.
Be sure to go downtown that day and enjoy yoursellf whether you will be an audience to some event or just watching the multitude of Icelandic people downtown Reykjavík.
You can take a look at the schedule
here.