I believe you're referring to ley lines maybe? which are lines drawn connecting ancient sites...
Or nav lines...which I'll quote from the profantasy tome of ultimate mapping:
Navigation lines (navlines) were used on early maps to give sailors waypoints and bearings
when traveling relatively short distances. They only appear over bodies of water. They give
a map an authentic historical look. If you prefer purely functional maps, you’ll probably want
to do without them.