Here's something that I found interesting as I've been working on the Blitzkrieg Peninsula of my World of Cinder: placing dragons. According to the chart on page 16 of OD&D volume 2, The Underworld & Wilderness Adventures, dragons can fly 24 five mile hexes per day. That's a 12 hex round trip. So assuming that dragons are territorial apex predators (which I do), that places a hard limit on how many flying dragons you can fit on any particular sandbox map. And looking over my particular map I can eyeball maybe three good places for dragon lairs. So from the moment this sandbox is put onto the table I'll be able to tell the players likely places they could hunt for dragon hoards. "Yeah, the Draco Mountains are called that for a reason." Stuff like that.
Of course those three lairs don't include long-hibernating wyrms forgotten by the races with shorter memories, dragons that have burrowed deep into the bowels of the earth or the Common Purple Land-dragon.