Wales - once upon a time... (about 40 years)

Hello UK!!
Two years ago, in April 2015 apeared under Riding/Rides and Stories a post  Scottlandtrip in May 2015. To cut a long story short: It was a very pleasant trip! 10 days, Heidelberg, Amsterdam, Newcastle, Drymen, Inverness, Kinross, Newcastle and back home.
In 2017 we like to travel to Wales. The reason is, in 1978 I spent 8 months at Castlemartin RAC Range with the German Army. You may imagine this time was themed: Young guys go west..!
With the memories of the Scottlandtour old Images of Wales, Pembroke, Camarthen and Pendine came up. Rather blurred. Best reason for sharpening and completing my memories. The first idea is visiting Pembroke and spot the region. May be "Lonely planet" includes some more advices. But real insidertips are only on hand by insiders.
Is there anybody out there who can help me?
Best regards from Heidelberg
Peter

Under the heading 'Visits' I think one to the Slate Mines in North Wales is essential, combined with trips on the Ffestiniog and Welsh Highland Railways.
In the same area is the fantastic hydro-electric power station inside the mountain, also a 'must' as far as I'm concerned.
Close by is Mount Snowdon. If you decide to take the train to the summit I'd advise travelling on the diesel-propelled one as the ride is far smoother than the steam-powered one.
Harlech Castle is a good one to visit but beware of the road up the hill beside it: steep, hair-pin and very smooth surface.