It was Queen Margrethe II 70th Birthday celebration. Because the royal family is so beloved in Denmark, the Queen's birthday is basically a national holiday. Stores are still open and most business goes on as usual but the roads in the city center shut down as the Queen makes her appearance on her balcony and then rides in her carriage to city hall.
For some reason one of the fountains in the city has real gold apples placed in it for the Queen's birthday. Two of the apples can be seen floating on the water spouts.