Try Potomac Pride, though it may not be as large as you want.

Some that come to mind are Jurassic Park, Puckered Giant, nigrescens, Elatior, Komodo Dragon, and Sea Monster. Don

Karen,

My mature Potomac Pride is pretty much the same size as your Blue Mountains and VERY dark. Not sure it gets as big as what you are looking for. Here is a recent picture.
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Nigrescens gets really big and is impressive. When we were at Tom Riddle's display garden this summer, that was the first hosta my DH ever expressed an keen interest in and we HAD to get one. More of a paler bluish-green, though, than what you're looking for, I think. Here is a photo of "our" baby Nigrescens. Sorry its a little blurry but so am I this morning...
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How about 3 big hostas? Niagara Falls on one side.... Potomac Pride in the center.... and Nigrescens on the other side? If there's room for 3 big ones. Niagara and Nigrescens have a more upright habit and Potomac more mounding...I can see it now...Put in a post for that red-tailed hawk to sit on and watch over your new bed...

Char

After thinking about it more, you don't want the shortest one in the middle. So now I vote for Niagara Falls only. Look at Papou's in a recent post...HOSTADILLY-GORGEOUS!

Char