Looking back to the far end of the amphitheater at Fort Rock, you can see that the far, higher-based walls have not been as modified by erosion as much as the cliffs at the "mouth" of the feature. They're above the high stand of the pluvial lake. I've always kind of assumed that the lower mound visible in the center, which stands farther out from the tuff ring than you can see in this photo, represents the last dying gasp of this eruption, but I never mapped it carefully enough to get real evidence for or against that conjecture. I will say, though, the feature overall shows the same circular structure, and strike-and-dip patterns, as Fort Rock overall. Had we an hour or two to spend here, there's a rough dirt road (not open to private vehicles) that circles the internal perimeter of this park, and is a moderately easy walk- that is, there are some decent grades in places, which may have one or two hundred feet elevation change, max, but overall, it's a pretty flat stroll. And with the road, you're not fighting through or weaving around the ubiquitous sage and rabbit brush. Even as out of shape as I am, I wouldn't hesitate to set out on the loop.
For the more adventurous, just out of frame to the left, there's a long, not-too-steep slope that allows safe and relatively easy access to the top of the rampart on its west flank. I didn't get a photo of that spot, but it's a pretty obvious and heavily used path, visible here. It's safe enough that we took high school groups up there (after a quick talk about common sense and sudden death); the views out over the valley floor are very much worth it. But at this point, between the physical exertion, growing fear of heights, and increasing difficulties with balance, I have a feeling it's not a spot I'll get back to.