I assume it's a person sitting in a wheel chair or ECV. I kind of wondered about the location of the wheel chair viewing area when I noticed how somebody seated in one sits head and shoulders and more above everyone else in the row. I wasn't directly behind the guest in the wheel chair in that spot on the day I visited, but I did wonder about the sight lines for those seated in the rows just behind that aisle separating the front orchestra from the back rows of the orchestra near where the wheel chair area was.