the secret is the use of Graduated Neutral Density filters
I don't use techniques of HDR,I use ND GRADS filters - http://www.singh-ray.com/grndgrads.html -,in the site you has a very detailed explanation of his use and of the obtained results.
The camera was the about 5,6 meters in a stone below,and I used the self-timer in 20 seconds to have the necessary time of to run to the top and to do the picture.
"After the first glass, you see things as you wish they were. After the second, you see things as they are not. Finally, you see things as they really are, which is the most horrible thing in the world."
--Oscar Wilde on Absinthe