John o' Groats is a village Scotland where Lewis, Uncle Jonathan, and Mrs. Zimmermann view the remains of, and take pots shots at, the Spanish Armada - albeit in one of Jonathan's illusions (The House with a Clock in its Walls, 73, 78).
John o' Groats is a village in the far north of Scotland. John o' Groats lies on Britain's northeastern tip, and is popular with tourists as one end of the longest distance between two inhabited British points on the mainland, with Land's End in Cornwall lying 876 miles (1,410 km) to the southwest. It is not quite the most northerly point on the island of Britain. The phrase "Land's End to John o' Groats" is frequently heard both as a literal journey (being the longest possible in Great Britain) and as a metaphor for great or all-encompassing distance, similar to the American phrase coast to coast.
- Wikipedia: John o' Groats