Stortorget is the name of this square in the centre of Gamla Stan, which is surrounded by old merchant's houses including the Stockholm Stock Exchange Building on the right (now where the Swedish Academy meets every year to choose the Nobel Prize winners in literature).
The square was the site of the Stockholm Bloodbath, where Swedish noblemen were massacred by the Danish King Christian II in November, 1520. The following revolt and civil war led to the dissolution of the Kalmar Union and the subsequent election of King Gustav I.