The Spiral Staircase in the Vatican Museums was designed by Giuseppe Momo in 1932 — we spent only half a day inside, which was definitely not long enough. I suggest putting aside at least a full day, if you’re planning on going there. Two preferably.
Oh, and buy a ticket online, on the Vatican Museums’ webpage (beware of intermediaries!), to skip the line completely!
Shot with Nikon D700 + Nikkor 14-24 mm f/2.8G: f/8, 1/50, ISO 1400, 14 mm.