The original D&D rules instruct referees to use the mapboard for the old Avalon Hill game Outdoor Survival when you want to go on spur-of-the-moment exploration adventures. There's nothing particularly special about the Outdoor Survival board, other than it's got some varied terrain and not a lot of other stuff junking up the display.
This here graphic is a small piece of the gameboard for the classic Avalon Hill wargame Blitzkrieg. The crisscrossed hexes are urban areas, the graphic effect used meant to suggest intersecting city streets. I happen to own a copy of the Blitzkrieg board but not the game itself. A couple of days ago I was looking at this map and it occurred to me that I should be looking at the white squares on those hexes instead of the black lines. As a series of crowded white squares those hexes look kinda like a patchwork of cultivated farmland. In other words, imagine those hexes are where farms are clustered around villages or castles. Bam! Instant D&D campaign map.
I've never been completely satisfied with the results of my original World of Cinder sandbox map. I can't draw for anything and as much as I like the paper I used (an original Judges Guild blank wilderness hexmap), the hexes are just a smidgeon too small to comfortably fit counters. So maybe this old board could be drafted into use as another part of my campaign setting.