In about a month I'll be leaving to hike across Spain for a couple weeks. I need to travel as light as possible as I have to carry everything for the entire trip on my back while hiking between 15 and 20 miles a day. This is probably a once in a lifetime trip for me so I want to bring my DSLR with me (6D). I've got a little point and shoot (s100), but I'd really rather have my DSLR for this experience.
So, with that in mind, I need help figuring out what one lens I should acquire/take. I'm imagining that my subjects will be a mix of the landscapes that I walk across, pictures of buildings/churches, pictures inside said buildings/churches, and random shots of people along the way. In a perfect world, I think my 24-70 could capture 90% of what I'd encounter (it did on my most recent trip to Africa... such a great lens). However, the 24-70 is just too dang heavy to have attached to my backpack strap all day. So, I'm thinking of a fast prime and letting my feet do the zooming as needed.
But, I'm also up for suggestions. I think for me, wider is better, and due to the various conditions I'll encounter something 2.8 or faster. Any thoughts?