Are these two sentences correct?

I think "best" would be preferable in the first sentence, as in, "Among the park's BEST attractions are huge canyons, cascading waterfalls, and clear blue lakes." Most works in the second sentence.

They are wrong -- as most everyone else stated. A double negative in a sentence doesn't really equal a positive, but those of us who are particular on the grammer we use, will often answer with --- "oh, then you want me to go?" or "what do you have?" Just don't use them, or people will think you to be iliterate. I ain't not got nothing more to say on this one . . . . UGH.

second one doesnt really make sense. I think it should be;

Geysers make THE MOST spectacular display as they roar high above the ground.

Well if you're excluding the capitalized BETTER and MOST and the period after waterfalls then they are fine.

Correctomundo! (:

Sound good to me !