I'm really blown away by these maps and diagrams created by Levi Walter Yaggy, and published in 1887 in his folio book Geographical Portfolio - Comprising Physical, Political, Geological, and Astronomical Geography. Each page was 2 by 3 feet and the large graphics were intended to be used in the classroom as a teaching aid.
I spent some time looking closely at them, reading the tiny labels for fish species and alpine zones and rock layers (there are high resolution scans here) and as diagrams they're clear and beautifully executed. But I'm also kind of captivated by the little worlds they seem to build. They feel mysterious and almost fantastical, with condensed, spiky mountain ranges poking above translucent oceans. I know the images are describing my own planet, but I can just as easily imagine them as maps to one of the strange worlds of an Ursula K. LeGuin or J.R.R. Tolkien novel. (My favorite kinds of books are the ones with maps on the endpapers.)
More about these on Collossal (where I first saw these - cheers to them), and you can find more of Yaggy’s work at the David Rumsey Map Collection.