It's a fossil, the old floor of a street in Selinunte, Sicily, where old temples still live. The shell, as a fossil, is one thing with the stone, so we see the pattern on both. Original shot in B/W, scanned + PS for sepia tone. thanks
This photo drew my attention before but I didn't comment it yet. Now I see it larger, I notice the pattern in the stones that continues in the shell! Did you do this, or did you notice it? It's great!
0 
