When the sun is in a position to stream through
the oculus of the Pantheon in Rome like
this, it's a time of day when you're likely to have
lots of company. But just look up and you can
almost feel like you're alone in this incredible place
—and it could be any time in the past +/- 2,000(!) years.
[To see more monochromes, visit Dragonstar's meme.]