First take a look at my smugmug.com gallery of Venice images and see if you like my style...
https://rpcrowe.smugmug.com/Architecture/Venice/
I shot these images with a pair of 7D cameras carrying a 17-55mm IS and a 70-200mm f/4L IS lens.
Out of the 90 images in this gallery I used the 17-55mm lens on 77 of them and the 70-200mm lens on the other 13. This count is not entirely accurate because I have a few duplicate images (color and B&W) and I did not sort out these dupes...
Here is my smugmug gallery of Istanbul images.
https://rpcrowe.smugmug.com/Other/Istanbul/
Out of the 167 images in this gallery, I used the 17-55mm lens for 110 of them and the 70-200mm for 57. (same thing goes for a few duplicates that I did in both color and B&W). This is closer to my normal ratio of about 2/3 of my shots with the 17-55mm lens and 1/3 with the 70-200mm...
I am thinking that the preponderance of Venice shots with the 17-55mm lens was due that city being a fairly close quarters environment for shooting. That might well be true for other cities of Italy...
BTW: a cheap way of "renting" a lens is to buy a used copy on eBay and then sell it on eBay when you return...
Another tip: A pair of double sided Velcro straps about a meter or a yard long can secure your monopod to some solid (parking meter, fence, etc) will give you a solid hold for a long exposure AND/OR carry an empty bean bag and fill it with rice or beans at your destination. Bean bags can be used in many places for a camera rest.
Finally... if you are a wide angle aficionado, the 12-24mm Tokina f4 Mkii lens is great and will not require to sell your first born child to buy...