I will be taking my first trip to Italy late this summer and will be visiting Rome, Florance, Chique Terre, and Venice. I'm hoping to pack light and will be traveling with my 5Diii and 24-105L at a minimum. I'm looking for some advice on a wide angle lens choice for the trip.

I would like to be able to capture good pics inside churches and in the small to large squares as well as the grand vistas like inside the coliseum. I will not be traveling with a tripod so that will make panos much more difficult.

I currently have the Canon 16-35L ii but I'm curious if this is the right choice. I've been eyeing the sigma 15mm fisheye for some time and thought that this might be a better choice?

My experience with the 16-35 with indoor and architecture shots is that perspective usually causes slanted walls and other distractions. Would I really be much worse off with a fisheye?

Thanks in advance for the advice!