A Rose line is any North South line.......like the one in Some's whorehouse.....straight down the center of the cafeteria.

Rose lines......to rose gardens..........famous church's to Some's whorehouse in NW, Wash DC....

Rose Line - Wikipedia

https://en.wikipedia.org/wiki/Rose_Line

 

Jump to The Da Vinci Code - The term Rose Line as the Paris Meridian was given by Dan ... gnomon in the Parisian church of Saint-Sulpice