The problem with long exposures is that while you stand there nonchalantly waiting for the exposure to be completed people may accidentally walk into the frame. It isn't always a bad thing and in this case I like the ghost of our guide. He is well into the foreground and I like that he happens to be looking up towards the cavernous domed ceiling above, his presence was a welcome surprise.
Canon 1D X, Canon 16-35/f2.8L Mark II
16mm, f5.6, 10 sec @ 320 ISO