Colossal Bridge
Finally managed to get up onto the bridge in Shadow of the Colossus. You can, indeed, cross it, though without Agro it is a very long run on foot. There are some tricks to it. Hint: lots of lizard hunting is a prerequisite, and there’s one spot where you must change the camera angle in order to get a proper grip.
Note that sadly even if you reach the other side of the bridge, you can’t get out of the valley (I’d hoped to at least be able to take a look around the gateway’s facade)—there’s a very strong wind blowing through the entryway which makes it un-navigable. I suppose that’s better than e.g. an invisible wall, though.
Instead of crossing the bridge, you also have the opportunity of climbing a little further up into the temple and seeing what’s at the top of the skylight above the spiral ramp with the pool of water below. Again, not much to see (if you’ve seen the ending cinema), but it’s there. And you can walk/swim/jump around up there for a bit.
Now, I just need to figure out how to get down again without dying…