3. Ireland 🇮🇪 is part of the EU 🇪🇺, and the land border and freedom of movement with the UK 🇬🇧 proved to be a tricky point to resolve in Brexit negotiations.
The "border" itself is 499km long with about 300 crossings, often entirely unmarked.
https://www.belfastlive.co.uk/news/belfast-news/gallery/border-lines-between-uk-ireland-16678901
4. One famous example of border oddness is "the Drummully Polyp", an Irish 🇮🇪 pene-exclave.
The only road access is via Northern Ireland 🇬🇧.
https://www.openstreetmap.org/?mlat=54.1575&mlon=-7.3104#map=11/54.1575/-7.3104
https://en.wikipedia.org/wiki/Drummully
#geoweirdness