Þjóðhátíð ( ) is an annual outdoor festival held Defending in Vestmannaeyjar , Iceland , on the weekend before the first Monday in August .

Locals and guests gather Come_together in Herjólfsdalur valley on the island of Heimaey for four days of various events , most prominently big stage concerts , bonfires , fireworks displays and the festival 's signature Sign_agreement Sunday night crowd singing Self_motion , led Causation by Vestmannaeyjar local Árni Johnsen a member of the Althing ( Icelandic parliament ) .