ABC Wednesday—X is for "what I see"

Seen in the crypt of the basilica of
San Miniato al Monte, in Florence: You
probably see crosses (very old ones,
as this church was begun in 1013 and the
interior has changed hardly at
all since it was first built).
I, however, choose to see X's—
or at least today I do.

[To see more ABC posts, go here.]