When i 1st saw this card, i thought this was an image of a sanctuary but i was wrong. This crowd is attending the Latvian Song and Dance Festival.
The Latvian Song and Dance Festival is an important event in Latvian culture and social life. The All-Latvian Song and Dance Festival has been held since 1873, normally every five years. During the festivals exhibitions of photography, art and folk craft, orchestra concerts, and a festive parade also take place. Events and competitions leading up to the event occur throughout the period between festivals.
Approximately 30,000 performers altogether participate in the event. Although usually folksongs and classical choir songs are sung, with emphasis on a cappella singing, recently modern popular songs have been incorporated into the repertoire.
The 24th Festival was held in July 2008. The main events were held in the Grand Stage of Mežaparks and in the Daugava Stadium in Riga. The next edition will take place in 2013. - in: wikipedia
Renars participated in the festival in 2003.