Indeed, the game has some pretty open scenes, for instance the colosseum. The game also has the best facial animations and vegetation I have seen so far.
Nevertheless, I fail to see how Ryse can be an argument in the assessment of the ESRAM architecture. It's 900p after all, and such limitations of render target sizes are precisely what most of us were expecting as a consequence of the XBO's memory architecture.
So are they fully explorable or are they just there for decoration and smoke and mirrors to disguise a small arena joined on to a corridor?