Locks and keys?

So I'm not doing so well on coming up with witty and interesting blog titles, and this one will be super short anyway, but on our quest to find a non-touristy restaurant in Sevilla tonight, we crossed the river, my first time on the bridge. All along the bridge there are locks locked to the railing and on the locks people have written their names and the names of their amantes, some have dates and some have hearts drawn on them. It was very romantic, or would have been had I been strolling along the river with an amante of my own. I'm left wondering, though, what do they do with the keys? Throw them in the river?