Here is a stronger start:
Once
each year, the Venetian people...
Using "each" instead of "a" is a good way to add "definition" to that first sentence.
In that first paragraph, you give some great descriptions, but it seems to be about 2 different subjects. One is that holiday, and the other is the beauty of Venice in general. I think it will be good if you take a more formal approach and put an intro paragraph before that initial paragraph of description. Tell the reader you are going to write about an experience in Venice that changed the way you think.
For example, you might want to switch the order of the first 2 paragraphs and make some modifications so that you give a very clear idea of what the essay will be about.
This can be improved also if you tell not just about the beauty and brilliance of the place but about the actual insights it gave you about life. In what way did it change your life? Do you now think differently about your career or academic aspirations? I think it will be good if you use less description and more reflection on how it changed you. HOWEVER, you really wrote very well in giving these descriptions.
Kevin, EssayForum.com