

At first, people used itinirary (to go to Rome, first go to PlaceX, then PlaceY, etc)
Maps of the time, when they existed, where merely illustrations, with fictionnal places sprinkled in.
Then some attempts mesured distances between places by counting step, and overall direction. This is why most maps before 1000ce are really strange looking, but you can guess what they represent using the name of places.
With the invention of things like the astrolab, people where able to mesure both distances and more precise direction, giving birth to triangulation, which was used until the invention of GPS




It might not be the most whimsical campain but it definitely fits and since you specified 3.5e (which I interpreted as somewhat old-shool), I would like to recommend Dolmenwood.
Is is built for OSE but it is closer to 3.5 than any content for 5e, so easily adaptable. It is a whole world with an hex-map filled with adventures and a few campains are provided. It takes place in a giant wood-land with some fey-wild shortcuts and has a good dose of whimsy (talking mushroom folks and the like)
I recommend you give it a look, I don’t know if it is the right fit for you but if it is, you have year of adventures ahead of you, ready in a book.