Every car, except for one (and not by much) is one of four colors: black, gray, red (also kind of specific red hue) and white.

What are the odds of this happening at a public parking place?

Hint: look at the cars.

Not even close…

Thinking about this, the only ancient information we are still able to access is painted or edged on stone or clay. How about some sort huge wall with thousands of QRcode like engravings?