In a 1990 seminar Derek Pearsall made a passing reference to the Gough Map, in a discussion of the journey Gawain makes across the realm of Logres, in Sir Gawain and the Green Knight.
The Gough Map is the oldest surviving road map of Great Britain, dating from around 1360. It’s roughly oblong in shape, made of two pieces of vellem, and is half map and half sketch. Not much is known about its provenance; the map was given to the Bodleian library in 1809 by its owner, Richard Gough. The dating is based on the inks and materials used to make the map, and on the place names.
691. Now rideȝ þis renk þurȝ þe ryalme of Logres,
692. Sir Gauan, on Godeȝ halue, þaȝ hym no gomen þoȝt.
693. Oft leudleȝ alone he lengez on nyȝtez
694. Þer he fonde noȝt hym byfore þe fare þat he lyked.
695. Hade he no fere bot his fole bi fryþez and dounez,
696. Ne no gome bot God bi gate wyþ to karp,
697. Til þat he neȝed ful neghe into þe Norþe Walez.
698. Alle þe iles of Anglesay on lyft half he haldez,
699. And farez; ouer þe fordez by þe forlondez,
700. Ouer at þe Holy Hede, til he hade eft bonk
701. In þe wyldrenesse of Wyrale; wonde þer bot lyte
702. Þat auþer God oþer gome wyþ goud hert louied.
703. And ay he frayned, as he ferde, at frekez þat he met,
704. If þay hade herde any karp of a knyȝt grene,
705. In any grounde þeraboute, of þe grene chapel;
706. And al nykked hym wyþ nay, þat neuer in her lyue
707. Þay seȝe neuer no segge þat watz of suche hwez
ETA: There’s now an official Gough Map site.