https://github.com/davepinch/pinchy.cc/blob/master/content/camera-roll/2025/01/2025-01-05/5-Railroad_bridge_over_the_Blackfoot_River_near_Milltown,_Montana.jpg.md
Octadecagon (Wikipedia) In geometry, an octadecagon (or octakaidecagon) or 18-gon is an eighteen-sided polygon.
https://commons.wikimedia.org/wiki/File:Railroad_bridge_over_the_Blackfoot_River_near_Milltown,_Montana.jpg
