Windows Live Local's image isn't as good but I think it shows a boat and barges traversing the locks of the Rideau Canal. To see what I'm talking about, go here and click back and forth between Google Maps and Microsoft VE (aerial).
Here's the wikipedia article and here's their web site.
From the Spirit of Canada web site:
The Tulip Festival has its origins in World War II when the late Princess Juliana (later to become Queen of the Netherlands) spent the war years in Ottawa. When peace came, she returned home; but she never forgot her stay in Canada. So each year, a gift of over 20,000 tulip bulbs is sent to Ottawa. This year (2005), the festival signals the 60th Anniversary of the end of the war and the Gift of Tulips to Canadians comes as 'A Celebration of Peace and Friendship'.