Bob very interesting map. Had to laugh at the Portuguese situation. Seems odd the way some Spaniards ignore Portugal not even considering it as another country when they visit.
Reminds me that recently there was a referendum in Catalunya about independence. I believe officially it is illegal but was tolerated. Overwhelming pro support as you would expect from the Catalans. But the point: In a bar in Madrid I heard “it can’t happen, it will ruin the shape of the country”. Maybe that important factor explains the need to include Portugal as their own

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Sam you set yourself a very stiff test but certainly a very enjoyable and rewarding one.
I find listening to Spaniards talking in interviews very difficult. In day to day conversation you can always say “un momento, no entiendo, ......” and when they know you are a foreigner they tend to tone down all that slang and regional variation. I’ve tried listening to flamencos being interviewed but it is largely beyond me.
Some bits of conversation I stumbled on were/are:
They shorten ‘ado’ to ‘ao’. That gives ‘lado’ as ‘lao’, ‘helado’ as ‘helao’ (‘ao’ as ‘ow’ in ‘How’ – apologies for terrible phonetics but hopefully you get it). I even use it now but it caught me out many times.
My wife being Sevillana but working 18 years in a Madrid maintenance aircraft hanger has a rare turn of phrase. But the one that sort of annoys me is when she refers to her mother, sisters, amigas, etc as ‘tio’. Why not ‘tia’. She of course refers to men as ‘tios’ as well.
Now I visit Asturias more than any other part of spain I am beginning to speak like them. One great advantage is they often drop the feminine and masculine so for example ‘gaitas’ become ‘gaites’. I love that because I quite often get my masculine and feminine the wrong way round.
But it is all great fun and you learn so much about the culture.
Good luck with it Sam but most of all hope you enjoy the journey as much as I am.