I was facing the front of the statue and shooting more or less straight up. The open vents or windows in the back of the statue are behind - toward the top of the frame. But the bars you see is not the window, but is the hand rail of a work scaffold. The view looks up into the statue's head (emptiness!) and you can see the bronze straps which were added to reinforce where it connects to the torso. Also, you see many 'dimples' which are the insides of the 656 "rohotsu" or hair curls on the head.
When first entering it is very hard to see until your eyes adjust, so you might miss a couple of things as you try to find your way in. One is a seated version of the guardian deity of the Yoritomo family (remember the First Shogun of Kamakura?). There is also an image of Yuten, a priest who restored the temple during the Edo period. A bronze tablet explains the work he accomplished.
Moody also mentioned a large pair of straw sandals (waraji). I read somewhere they were donated by school children in Ibaraki, but Moody heard they came from Kashima Jingu Shrine. I don't really know. Either way they are from Ibaraki Prefecture and they are big - 2.8 meters long (over 9 feet), the size this statue would wear. A message with the sandals reads "Buddha must surely be tired after sitting there for some 700 years and we would be very pleased if he would wear these sandals when he takes a walk."
Thanks to Moody. As Art Baker and then Jack Smith used to say on American TV when I was a kid, "You Asked For It!"