Rotterdam has a number of festivals that attract hundreds of thousands of visitors. The Summer Carnival is probably the most popular one. It is organized every year on the last Saturday of July. This year it was once again one big party; it did not really matter that the weather was not supportive.
For the streetphotographers amongst us: You should reserve this date for next year. This event is a great opportunity for all streetphotographers to get some nice shots and practice your skills.