Your vision is clearly epic in scale, that much is made clear enough by the lively green mountains being cut by water and sunshine's rays falling on all beneath lightly clouded skies. The castle with its own waterfall is beautiful, although could probably have been drawn up to look a little bit more fantasty (taller towers, structures around waterfall, etc). There is a excellent shadowed town/castle on the right of the picture that wasnt noticeable until closer inspection (which is good because it means that the longer u look the more there is to find.) Honestly, the impact of the piece made me feel humble and peaceful.
I enjoy your technique in making the piece appear to be similar to an impressionistic painting which have always used bright vivid blues, yellows, and greens. This adds to the feeling of nature that you were surely going for.
My only improvement that I could suggest would be to fill in areas of the picture with action, such as structures around the waterfalls, a person walking the path on the right or standing in front of the mouth of a cave on the right, boats in the river, or a bridge spanning the gap.