Comments: 4
... and yet, neither of them is called Merlin. Inconceivable!
or Owain Glydwr, for that matter.

I didn't make it far enough west down on the coast to get anywhere near Merlin's supposed crystal cave this past July (hoping to remedy that on my next trip), but I did manage to squeeze in a visit to Glynd┼Ár. But for a meeting hall bearing his name, not a trace to be seen indicating he's remembered at all. Same thing with Llewellyn's grave, incidentally. It's still there, but if you don't know where to look on your own, there certainly isn't anything to guide you in the right direction ...
Well, it's known as The Parliament House iirc. Maybe everyone in Machynlleth believes the whole world knows its they should! ;-)